gallium: Move xorg drivers to targets

gallium: Move xorg drivers to targets

Attached output from git commit:
 rename src/gallium/{winsys/drm/intel/xorg => targets/xorg-i915}/Makefile (95%)
 rename src/gallium/{winsys/drm/intel/xorg => targets/xorg-i915}/intel_xorg.c (98%)
 rename src/gallium/{winsys/drm/i965/xorg => targets/xorg-i965}/Makefile (78%)
 rename src/gallium/{winsys/drm/i965/xorg => targets/xorg-i965}/intel_xorg.c (98%)
 rename src/gallium/{winsys/drm/nouveau/xorg => targets/xorg-nouveau}/Makefile (96%)
 rename src/gallium/{winsys/drm/nouveau/xorg => targets/xorg-nouveau}/nouveau_xorg.c (98%)
 rename src/gallium/{winsys/drm/radeon/xorg => targets/xorg-radeon}/Makefile (73%)
 rename src/gallium/{winsys/drm/radeon/xorg => targets/xorg-radeon}/radeon_xorg.c (98%)
 rename src/gallium/{winsys/drm/vmware/xorg => targets/xorg-vmwgfx}/Makefile (97%)
 rename src/gallium/{winsys/drm/vmware/xorg => targets/xorg-vmwgfx}/SConscript (100%)
 rename src/gallium/{winsys/drm/vmware/xorg => targets/xorg-vmwgfx}/vmw_driver.h (100%)
 rename src/gallium/{winsys/drm/vmware/xorg => targets/xorg-vmwgfx}/vmw_hook.h (100%)
 rename src/gallium/{winsys/drm/vmware/xorg => targets/xorg-vmwgfx}/vmw_ioctl.c (99%)
 rename src/gallium/{winsys/drm/vmware/xorg => targets/xorg-vmwgfx}/vmw_screen.c (100%)
 rename src/gallium/{winsys/drm/vmware/xorg => targets/xorg-vmwgfx}/vmw_video.c (99%)
 rename src/gallium/{winsys/drm/vmware/xorg => targets/xorg-vmwgfx}/vmw_xorg.c (100%)