Feature: #7: VSync

- Add VSync feature. 3 possible VSync methods available: "sw" (software,
  not too reliable, but at least you have something to fallback to),
  "drm" (using DRM_IOCTL_WAIT_VBLANK, should work only on DRI drivers),
  "opengl" (using SGI_swap_control extension OpenGL, might work on more
  drivers than the DRM method). "sw" and "opengl" are briefly tested,
  "drm" received utterly no test (because I use the nVidia binary blob).
  They are enabled with "--vsync sw" / "--vsync drm" / "--vsync opengl".

- Add --refresh-rate to let user specify a refresh rate for software
  VSync, in case the automatic refresh rate detection does not work
  well.

- Seemingly the automatic refresh rate detection using X RandR in
  software VSync detects refresh rate incorrectly. Need further investigation.

- Fix a few bugs in fading timing.

- Add a workaround for client window detection on Fluxbox, as Fluxbox
  (incorrectly?) sets the override-redirect flag upon all frame
  windows.

- Software VSync adds dependency on librt (a part of glibc) for
  nanosecond-level timing functions, and libXrandr for automatic refresh
  rate detection; DRM VSync adds dependency on libdrm to use its drm.h,
  but does not link to libdrm; OpenGL VSync adds dependency on libGL.

- Print timing information on DEBUG_REPAINT.

Makefile

@@ -4,8 +4,8 @@ PREFIX ?= /usr
 BINDIR ?= $(PREFIX)/bin
 MANDIR ?= $(PREFIX)/share/man/man1
 
-PACKAGES = x11 xcomposite xfixes xdamage xrender xext
-LIBS = -lm
+PACKAGES = x11 xcomposite xfixes xdamage xrender xext xrandr
+LIBS = -lm -lrt
 INCS =
 
 # Parse configuration flags
@@ -29,6 +29,15 @@ ifeq "$(NO_REGEX_PCRE)" ""
 	endif
 endif
 
+ifeq "$(NO_VSYNC_DRM)" ""
+	CFG += -DCONFIG_VSYNC_DRM
+endif
+
+ifeq "$(NO_VSYNC_OPENGL)" ""
+	CFG += -DCONFIG_VSYNC_OPENGL
+	LIBS += -lGL
+endif
+
 CFLAGS += $(CFG)
 
 LIBS += $(shell pkg-config --libs $(PACKAGES))