Reduces number of implicit integer conversions.

Didn't compile on GLib < 2.16.

This is easier and more efficient to loop on, because only two
variables get modified (src and dest).

GLib's macros are implemented with inline assembly, and probably a lot
faster than our naive bit shifting implementation.

The other audio_format attributes are not used.

This function is too complex for being inlined everywhere.

Send another "magic" MIME type when the byte order must be reversed.
This also fixes byte order issues when big-endian was involved (input
data or host byte order) - that was completely broken.

This function is not critical for performance, and the inline
expansion looks too expensive.

For better optimization.

Compile the plugins only once with the same C flags.

Prepare for enabling "silent-rules".

Don't use MPC_CFLAGS, MPD_LIBS.

Don't use MPD_LIBS, MPC_CFLAGS.

Don't use MPD_LIBS.

In a C file, that is too late, because _mingw.h defaults to 0x0502,
and ours would be illegal redefintion.

Use DESPOTIFY_LIBS in Makefile.am instead.  Also, use
DESPOTIFY_CFLAGS.

gprof is obsolete, it's better to use perfcounters in every aspect.

AC_SEARCH_LIBS allows the function to be present in libc.