Revert "Remove xrender-sync and xrender-sync-fence"

This reverts commit 50e2259404.

Temporarily revert the removal until we have more information about this whole
thing.

Turns out a couple of drivers don't work properly without the sync fence,
including intel, llvmpipe and NVIDIA.

Although sync fence is needed, from the information I have gathered (looking
at old bug reports, protocol specifications, look at other compositors' code),
compton's usage of it is not proper. So we need to rewrite it in the future,
after we get more information from driver developers.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/meson.build

@@ -4,10 +4,10 @@ deps = [
 	dependency('xcb', version: '>=1.9.2')
 ]
 
-cflags = [ ]
-
 srcs = ['compton.c', 'win.c', 'c2.c', 'x.c', 'config.c', 'diagnostic.c']
 
+cflags = []
+
 required_package = [
 	'x11', 'x11-xcb', 'xcb-renderutil',
 	'xcb-render', 'xcb-damage', 'xcb-randr',