Rip out old workarounds, hacks and macros for newer C++ features not being supported back in the day.

Adds LL_COMPILE_TIME_MESSAGE support to Linux.

llfinite -> std::isfinite
llisnan -> std::isnan
vector_shrink_to_fit -> vector.shrink_to_fit

indra/llmessage/llbufferstream.h

@@ -48,10 +48,8 @@ public:
 	virtual ~LLBufferStreamBuf();
 
 protected:
-#if( LL_WINDOWS || __GNUC__ > 2 )
 	typedef std::streambuf::pos_type pos_type;
 	typedef std::streambuf::off_type off_type;
-#endif
 
 	/* @name streambuf vrtual implementations
 	 */
@@ -87,17 +85,10 @@ protected:
 	 * or both masked together.
 	 * @return Returns the new position or an invalid position on failure.
 	 */
-#if( LL_WINDOWS || __GNUC__ > 2)
 	virtual pos_type seekoff(
 		off_type off,
 		std::ios::seekdir way,
 		std::ios::openmode which);
-#else
-	virtual streampos seekoff(
-		streamoff off,
-		std::ios::seekdir way,
-		std::ios::openmode which);
-#endif
 
 	/*
 	 * @brief Get s sequence of characters from the input