add XV renderer. TODO: ImageConverter should output yuv data
initialize xvimage. use ugly rgb->yuv in XVRenderer

performance is bad now
Merge branch 'master' into x11
force recheck if FFmpeg not detected

TODO: should we only recheck the part not pass the test?
fix qmake warning for back slash.

a back slash is '\\' for qmake
Add missing config test
Merge branch 'master' into x11

Conflicts:
	QtAV.pro
xv: black background
Merge branch 'x11'
GraphicsItemRenderer use the same painting logic and api with others
GraphicsItemRenderer aspect ratio change state

It's seems right. but why other renderer do not have this problem?
qmake: correct Qt version detection. do not empty cache if recheck
gl: check gl1 support
do not add qt opengl module if gl test failed
Merge branch 'gl'
README: building, player usage, FFmpeg projects etc
gl: do not include GLWidgetRenderer.h if gl is disabled

link error with msvc. why gcc is ok?
README: building QtAV
Fix compile warning about size_t
fix debug linking

the debug library name is wrong. why i commented that line before?