Restore change to _DRM_VBLANK_SIGNAL from rev. 1.41, which was reverted
drwxr-xr-x - bsd-core
drwxr-xr-x - bsd
drwxr-xr-x - libdrm
drwxr-xr-x - linux-core
drwxr-xr-x - linux
drwxr-xr-x - shared-core
drwxr-xr-x - shared
drwxr-xr-x - tests