Merge pull request #1310 from seanpaultaylor/next

Fixed bug related to FrameBuffer width/height goes out of date.
Removed redundant constructor
Add GTK-based DisplayFileDialog implementation for Linux
Merge pull request #1313 from rlofc/next

Added GTK-based displayFileDialog implementation for Linux
Makes GTK non-optional for PlatformLinux displayFileDialog.
Removes unused Social defs.