x11/cl-clx: Update to 0.7.6

Changes in CLX 0.7.6

• Introduce rudimentary LICENSE file
• Enable CLX for LispWorks 8.x and later
• BUFFER-READ-DEFAULT handles gracefully eof and partial reads
• RENDER-FREE-GLYPHS accepts START and END arguments
• Export a new convenience function FIND-STANDARD-PICTURE-FORMAT
• Fix RR-GET-SCREEN-INFO rates
• Initial port for ABCL
• Various fixes for bundled demos
• Document composite extension
• Export COMPOSITE-RELEASE-OVERLAY-WINDOW
• Portability fixes for multiple Common Lisp implementations
• Merge support for CLASP
• Merge support for CMUCL
• Cleanup of dependents and removal of obsolete kludges
• Export RENDER-SET-PICTURE-TRANSFORM
• Implement all render triangle functions from XRender

Sponsored by: The FreeBSD Foundation