libopenmpt 0.3 deprecates openmpt_module_create_from_memory() and
provides a replacement function openmpt_module_create_from_memory2().

Detecting libopenmpt 0.3 can be done at build time via the API
version macros provided by libopenmpt. libopenmpt 0.2 did not provide
all required macros, however libopenmpt documents the required #define
shims that can be safely added for libopenmpt 0.2.

Using openmpt_module_create_from_memory2() instead of
openmpt_module_create_from_memory() avoids the deprecation warning
when building ffmpeg with libopenmpt 0.3.

openmpt_module_create_from_memory2() provides more fine-grained error
reporting and in particular allows distinguishing out-of-memory from
input file parsing errors. Return appropriate ffmpeg errors
accordingly.

libopenmpt 0.3 is ABI and API compatible with applications built
against libopenmpt 0.2. Building ffmpeg with libopenmpt 0.2 is still
supported.

Signed-off-by: Jörn Heusipp <osmanx@problemloesungsmaschine.de>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>