2.6 vs 2.7

[mean]

The current dev branch is 2.7
It contains an up to date ffmpeg + better support for HEVC 10 bits + can be compiled with visual c++ with most of the asm code enabled

**BUT** It is likely to be broken in some minor or major ways, now or later

The 2.6_support branch (and nighties) contains the last release of avidemux + backport of the interestsing and not risky changes

In the nightlies
xxx_support = 2.6 + fixes
xxxx = 2.7, use at your own risk