Update/Modernize LLAvatarName and LLAvatarNameCache and _EVERYTHING_ they touch

Fairly certain this adds the feature in which the user may click the online notification to open a chat with the user coming online.

Translators may want to look at the xml changes of this change to see what to update

Removes old LegacyMultiAttachmentSupport patch
Moves LLAvatarName-centric functions into LLAvatarName from elsewhere.
Adds boost::signals2::connections to name polling places.
Removes more old icky static callbacks
Merge from Alchemy, credit where due~
Update notifications.xml to have a bunch of the tags from upstream to ease diffing

indra/llmessage/llavatarname.cpp

@@ -30,6 +30,7 @@
 #include "llavatarname.h"
 
 #include "lldate.h"
+#include "llframetimer.h"
 #include "llsd.h"
 
 // Store these in pre-built std::strings to avoid memory allocations in
@@ -42,6 +43,15 @@ static const std::string IS_DISPLAY_NAME_DEFAULT("is_display_name_default");
 static const std::string DISPLAY_NAME_EXPIRES("display_name_expires");
 static const std::string DISPLAY_NAME_NEXT_UPDATE("display_name_next_update");
 
+bool LLAvatarName::sUseDisplayNames = true;
+bool LLAvatarName::sUseUsernames = true;
+
+// Minimum time-to-live (in seconds) for a name entry.
+// Avatar name should always guarantee to expire reasonably soon by default
+// so if the failure to get a valid expiration time was due to something temporary
+// we will eventually request and get the right data.
+const F64 MIN_ENTRY_LIFETIME = 60.0;
+
 LLAvatarName::LLAvatarName()
 :	mUsername(),
 	mDisplayName(),
@@ -61,6 +71,27 @@ bool LLAvatarName::operator<(const LLAvatarName& rhs) const
 		return mUsername < rhs.mUsername;
 }
 
+//static
+void LLAvatarName::setUseDisplayNames(bool use)
+{
+	sUseDisplayNames = use;
+}
+//static
+bool LLAvatarName::useDisplayNames()
+{
+	return sUseDisplayNames;
+}
+
+void LLAvatarName::setUseUsernames(bool use)
+{
+	sUseUsernames = use;
+}
+
+bool LLAvatarName::useUsernames()
+{
+	return sUseUsernames;
+}
+
 LLSD LLAvatarName::asLLSD() const
 {
 	LLSD sd;
@@ -85,27 +116,90 @@ void LLAvatarName::fromLLSD(const LLSD& sd)
 	mExpires = expires.secondsSinceEpoch();
 	LLDate next_update = sd[DISPLAY_NAME_NEXT_UPDATE];
 	mNextUpdate = next_update.secondsSinceEpoch();
+
+	// Some avatars don't have explicit display names set. Force a legible display name here.
+	if (mDisplayName.empty())
+	{
+		mDisplayName = mUsername;
+	}
+}
+
+// Transform a string (typically provided by the legacy service) into a decent
+// avatar name instance.
+void LLAvatarName::fromString(const std::string& full_name)
+{
+	mDisplayName = full_name;
+	std::string::size_type index = full_name.find(' ');
+	if (index != std::string::npos)
+	{
+		// The name is in 2 parts (first last)
+		mLegacyFirstName = full_name.substr(0, index);
+		mLegacyLastName = full_name.substr(index+1);
+		if (mLegacyLastName != "Resident")
+		{
+			mUsername = mLegacyFirstName + "." + mLegacyLastName;
+			mDisplayName = full_name;
+			LLStringUtil::toLower(mUsername);
+		}
+		else
+		{
+			// Very old names do have a dummy "Resident" last name
+			// that we choose to hide from users.
+			mUsername = mLegacyFirstName;
+			mDisplayName = mLegacyFirstName;
+		}
+	}
+	else
+	{
+		mLegacyFirstName = full_name;
+		mLegacyLastName = "";
+		mUsername = full_name;
+		mDisplayName = full_name;
+	}
+	mIsDisplayNameDefault = true;
+	mIsTemporaryName = true;
+	setExpires(MIN_ENTRY_LIFETIME);
+}
+
+void LLAvatarName::setExpires(F64 expires)
+{
+	mExpires = LLFrameTimer::getTotalSeconds() + expires;
 }
 
 std::string LLAvatarName::getCompleteName(bool linefeed) const
 {
 	std::string name;
-	if (mUsername.empty() || mIsDisplayNameDefault)
-	// If the display name feature is off
-	// OR this particular display name is defaulted (i.e. based on user name),
-	// then display only the easier to read instance of the person's name.
+	if (sUseDisplayNames)
 	{
-		name = mDisplayName;
+		if (mUsername.empty() || mIsDisplayNameDefault)
+		{
+			// If this particular display name is defaulted (i.e. based on user name),
+			// then display only the easier to read instance of the person's name.
+			name = mDisplayName;
+		}
+		else
+		{
+			name = mDisplayName;
+			if (sUseUsernames)
+			{
+				name += (linefeed ? "\n(" : " (") + mUsername + ")";
+			}
+		}
 	}
 	else
 	{
-		name = mDisplayName + (linefeed ? "\n(" : " (") + mUsername + ")";
+		name = getUserName();
 	}
 	return name;
 }
 
 std::string LLAvatarName::getLegacyName() const
 {
+	if (mLegacyFirstName.empty() && mLegacyLastName.empty()) // display names disabled?
+	{
+		return mDisplayName;
+	}
+
 	std::string name;
 	name.reserve( mLegacyFirstName.size() + 1 + mLegacyLastName.size() );
 	name = mLegacyFirstName;
@@ -113,3 +207,48 @@ std::string LLAvatarName::getLegacyName() const
 	name += mLegacyLastName;
 	return name;
 }
+
+std::string LLAvatarName::getDisplayName() const
+{
+	if (sUseDisplayNames)
+	{
+		return mDisplayName;
+	}
+	else
+	{
+		return getUserName();
+	}
+}
+
+std::string LLAvatarName::getUserName() const
+{
+	std::string name;
+	if (mLegacyLastName.empty() /*|| (mLegacyLastName == "Resident")*/) // <alchemy/>
+	{
+		if (mLegacyFirstName.empty())
+		{
+			// If we cannot create a user name from the legacy strings, use the display name
+			name = mDisplayName;
+		}
+		else
+		{
+			// The last name might be empty if it defaulted to "Resident"
+			name = mLegacyFirstName;
+		}
+	}
+	else
+	{
+		name = mLegacyFirstName + " " + mLegacyLastName;
+	}
+	return name;
+}
+
+void LLAvatarName::dump() const
+{
+	LL_DEBUGS("AvNameCache") << "LLAvatarName: "
+	                         << "user '" << mUsername << "' "
+							 << "display '" << mDisplayName << "' "
+	                         << "expires in " << mExpires - LLFrameTimer::getTotalSeconds() << " seconds"
+							 << LL_ENDL;
+}
+