MusicPlus: Implement libopenmpt for better MOD playback

Better MOD playback! Fixes loop problems identified by Nev3r. Also lets you select instrument filtering.

In future, this lets us mute channels and do other cool shit.

SteelTitanium wrote the original code.

Implementation

• The binaries require MSVC 2015 runtime. Because we don't want to force this on the user, they are loaded optionally. If they are not available, the game falls back on SDL Mixer for MOD playback.
• Builds by default on Windows; on Linux, must opt-in by passing OPENMPT=1 into make.
• No buildbot support yet, because the distros are too old and they don't have libopenmpt-dev.

changed the description

mentioned in merge request !1 (closed)

added 864 commits

• 4b4bd638...7916e020 - 837 commits from branch public-musicplus-core
• 0b857f12 - Update capslock state on window re-focus
• 6dddf612 - Target nocona for 64-bit builds
• 4a05fd5f - More explict check
• 5ba08638 - Stupid restrictions
• d048e7cb - Don't set if LINUX64 is defined
• 4cfacf5c - Check for NONX86 in addition to X86_64; move MINGW64 subflags from win32/Makefile.cfg to Makefile
• 3d2e5886 - Rename M5 to ARCHOPTS; allow override by command line
• 34534428 - Add 64-bit SDL builds to appveyor config
• 2aa7ee70 - Disable UPX by default in appveyor
• 0fc07eba - Consolidate [%CONFIGURATION%] == [SDL64] into %X86_64%
• e7165444 - Add 64-bit DD buildbot
• bef0bc82 - Merge branch 'mingw-64bit-cpu-target-revise' into appveyor-64
• 941e2978 - Implement install building for appveyor (deployer)
• e1300d51 - Rename ASSET_PATCH_DLL_GET to PACKAGE_PATCH_DLL_GET
• f00cfb7b - Use optional asset archive instead of file
• bd81c319 - Merge branch 'appveyor-deployer' into 'appveyor-64'
• ce7875b1 - Merge branch 'appveyor-64' into 'mingw-64bit-cpu-target-revise'
• bbd878e5 - Merge branch 'mingw-64bit-cpu-target-revise' into 'master'
• 528c6f77 - Make AppVeyor installer paths consistent with Travis installer…
• 900a439c - Merge branch 'appveyor-installer-revise' into 'master'
• 5278d1ca - Merge branch 'caps-lock-consistency-fix' into 'master'
• 6166fad0 - Merge branch 'public-musicplus-core' into public-musicplus-libopenmpt
• 109dd70a - Merge remote-tracking branch 'public-gl/master' into public-musicplus-core
• 953f5b62 - Merge branch 'public-musicplus-core' into public-musicplus-libopenmpt
• 7f184330 - Update libopenmpt dev library to 0.4.0 (winold.vs2017)
• 08812b15 - Revised MinGW Makefile logic for OpenMPT
• a851c5d7 - Add libopenmpt to cmake

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added 6 commits

• 2e0e0a38 - musicplus-le-changemusic 2.2 -> 2.1 backport
• d4cef2bf - Merge branch 'public-musicplus-core' into public-musicplus-le-changemusic
• 17fc39c6 - Merge branch 'public-musicplus-core' into public-musicplus-le-changemusic
• 72907234 - Merge branch 'public-musicplus-core' into public-musicplus-le-changemusic
• 1aacfee8 - Merge branch 'public-musicplus-le-changemusic' into public-musicplus-core
• c8d338ca - Merge branch 'public-musicplus-core' into public-musicplus-libopenmpt

Compare with previous version

added 2 commits

• e2e34598 - 1 commit from branch public-musicplus-core
• dd856a8c - Merge branch 'public-musicplus-core' into public-musicplus-libopenmpt

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