add undocumented option --apply-replaygain-which-is-not-lossless to flac; required a lot of reorganization; gain_analysis lib renamed to replaygain_analyis; replaygain_synthesis moved out of plugin_common into its own library in share/

built and can they be portably linked into shared libraries.

revamp MSVC build system, separate dynamic and static builds, separate debug and release intermediate directories