Configure: provide a switch to build for a "Windows Store App" target

"Windows Store App" are what we used to call Metro Apps, or Modern UI
apps.
They are apps without HWMD and without Console
Win32: disable IPC in WinStoreApp mode

IPC and one instance depends on HWND and calls will fail.
Win32: disable Console output of help in WSA mode

Calling AllocConsole does not work all the time in Metro mode,
and is supposed to be an undefined behaviour.
Win32: check AllocConsole() return value
Win32: set default clock-source on multimedia, for now

It seems to be better for the machines with lying power-improvement
programs, like ASUS EPU-Engine
Win32: use GetNativeSystemInfo to get the processor count
Allow overriding _WIN32_WINNT with environment variable
Allow overriding _WIN32_WINNT through CPPFLAGS

Suggested-by: Rémi Denis-Courmont
FLAC: fix 7 channels layout

See http://flac.sourceforge.net/format.html
avcodec: reuse AVFrames so no need to allocate/free it every time we encode picture/audioblock
x264: enable setting fullrange flag and input
TS: insert/flag PAT/PMT before keyframes if use-keyframes is set

Flagging those PAT/PMT blocks enables us to segment ts-files so that
each segment starts with PAT,PMT,Keyframes. Usable in livehttp-module.
livehttp: split from PAT/PMT that precedes keyframes instead of keyframe
Qt: PLSelector: add customized icons
auhal: implement TimeGet for the analog part
XCB: merge GetWindowSize() into GetWindow()

This saves one geometry request and some code.
XCB/GLX: reuse windowing code from other XCB plugins
auhal: replace deprecated CarbonCore calls introduced in Component Manager 3.0 back in 1994 with their modern counterparts

requires 10.6 or later
auhal: fix a few compilation warnings
auhal: remove Carbon dependency