Revert removal of overflow2 use in gd.c
Function provided by gd_security with bundled libgd
Function provided by gd_compat with system libgd

This fix failed test imageloadfont_invalid.phpt
This test now also pass with system libgd
Merge branch 'PHP-5.5'

* PHP-5.5:
  Revert removal of overflow2 use in gd.c Function provided by gd_security with bundled libgd Function provided by gd_compat with system libgd