libmpq is a much simpler alternative to StormLib for reading MPQ archives.
We use our own fork of libmpq: https://github.com/diasurgical/libmpq
Impact:
* DevilutionX is now a lot more portable. Unlike StormLib, libmpq only
needs platform-specific code for Windows.
* Locks around file access **removed** (instead we duplicate the file descriptor for streamed audio only).
* RAM usage is **300 KiB** lower than StormLib.
* Stripped release linux_x86_64 binary is **32 KiB** smaller.
* Amiga build now hangs instead of crashing.
Previously, we always loaded entire videos in memory before playing them.
`libsmacker` does not provide a streaming API but it does provide a
`FILE *` file pointer API.
We now take advantage of the `FILE *` API by streaming the videos on
platforms that support `fopencookie`.
This means faster startup and less memory usage on these platforms.
Gleb Mazovetskiy
Anders Jenbo
staphen