Ensure api_conv.pl is idempotent on names of constants: XCB_[A-Z0-9_]+.
Ensure api_conv.pl is idempotent on names of constants: XCB_[A-Z0-9_]+.

OpenInkpot-archive/iplinux-libxcb,topcat/xcb-win32,stapelberg/libxcb,topcat/xcb-win32,topcat/xcb-win32,topcat/xcb-win32,topcat/xcb-win32,OpenInkpot-archive/iplinux-libxcb,stapelberg/libxcb,OpenInkpot-archive/iplinux-libxcb,stapelberg/libxcb