Make global strerr() functions in llfile.cpp static member functions of LLFile.

This is the cleanest way to make them available to the rest of the
viewer as exported functions.

This change is needed for / use by AIMultiGrid.

indra/llcommon/llfile.cpp

@@ -49,7 +49,8 @@ static std::string empty;
 
 #if LL_WINDOWS
 // On Windows, use strerror_s().
-std::string strerr(int errn)
+//static
+std::string LLFile::strerr(int errn)
 {
 	char buffer[256];
 	strerror_s(buffer, errn);       // infers sizeof(buffer) -- love it!
@@ -98,7 +99,8 @@ std::string message_from(int orig_errno, const char* buffer, size_t bufflen,
 					 << " (error " << stre_errno << ')');
 }
 
-std::string strerr(int errn)
+//static
+std::string LLFile::strerr(int errn)
 {
 	char buffer[256];
 	// Select message_from() function matching the strerror_r() we have on hand.
@@ -108,7 +110,8 @@ std::string strerr(int errn)
 #endif	// ! LL_WINDOWS
 
 // On either system, shorthand call just infers global 'errno'.
-std::string strerr()
+//static
+std::string LLFile::strerr()
 {
 	return strerr(errno);
 }
@@ -125,7 +128,7 @@ int warnif(const std::string& desc, const std::string& filename, int rc, int acc
 		if (errn != accept)
 		{
 			LL_WARNS("LLFile") << "Couldn't " << desc << " '" << filename
-							   << "' (errno " << errn << "): " << strerr(errn) << LL_ENDL;
+							   << "' (errno " << errn << "): " << LLFile::strerr(errn) << LL_ENDL;
 		}
 #if 0 && LL_WINDOWS                 // turn on to debug file-locking problems
 		// If the problem is "Permission denied," maybe it's because another

indra/llcommon/llfile.h

@@ -82,6 +82,9 @@ public:
 			std::ios::openmode mode);
 
 	static  const char * tmpdir();
+
+	static std::string strerr(int errn);
+	static std::string strerr();
 };
 
 /**