0027097: GCC and CLang compiler warnings and errors with -Wpedantic

Useless semicolons are removed after closing braces of namespaces and macros in code dependent on FreeImage and VTK.
Comments added at the closing braces of namespaces to help comprehension.
In OSD_File.cxx and OSD_Disk.cxx, unnecessary declarations of system functions are removed

src/Font/Font_FontMgr.cxx

@@ -173,7 +173,7 @@ static const Font_FontMgr_FontAliasMapNode Font_FontMgr_MapOfFontsAliases[] =
       }
     }
 
-  }
+  } // anonymous namespace
 
 #endif