fix link issue of loudness executable module on MinGW

Since libscanner-common.a is passed *after* GLib libraries to the linker,
MinGW linker cannot resolve dependency of libscanner-common.a on GLib.
This fix explicitly declares dependency on GLib in scanner-common
CMakeList.
fix build issue of libinput_sndfile on MinGW

Dependent libraries set by set_target_properties() + LINK_FLAGS is
passed to the linker before our objects in linker command line,
therefore MinGW linker cannot resolve dependendy.
This fix use set_target_properties() only to set *FLAGS_OTHER, and
use standard way for setting library related information.
fix compile issue on input_ffmpeg

AV_CH_* requires audioconvert.h or channel_layout.h on recent libav
av_find_stream_info() -> avformat_find_stream_info()

av_find_stream_info() is deprecated, and missing from recent libav
fix link issue of libinput_ffmpeg on MinGW

Same as libinput_sndfile. set_target_properties() + LINK_FLAGS result in
improperly ordered linker argument.
Merge pull request #4 from nu774/mingw_build_fix

Mingw build fix