Set 640 permission on (750) import files
Fix errors on build GL3:

Errors in ../import/derelict/opengl3/glxext.d(51):
Error: struct derelict.opengl3.glxext.__GLXFBConfigRec unknown size
Error: struct derelict.opengl3.glxext.__GLXFBConfigRec no size yet for forward reference
Merge pull request #156 from vsn4ik/master

Сorrected permissions and fix errors on build GL3