Sync with draft -14
Minor doc improvement wrt OPUS_APPLICATION_RESTRICTED_LOWDELAY.
Move the various version defines to be together.

The config.h version defines were declared in the
middle of the math feature testing. This commit moves
it to the top of configure.ac where the other version
number code resides.
Remove the obsolete LIBOPUS_SUFFIX define.

As best we recall, this was used to version the
library filename during rapid development. It's
no longer needed now that the bitstream is frozen
and isn't hooked up to anything in the build system.
int vs opus_int32 consistency
Tweak doxygen input so that the manpage names won't conflict.
Actually install the documentation with make install

Instead of just its build stamp :)
Enable building just the library (or just the docs)

Both are still built and installed by default though.
Use 'frame' instead of 'signal', take out stdlib.h in silk/.

On MacOS, stdlib.h ends up including sys/signal.h, generating
warnings about the local variables called 'signal' shadowing
the global symbol signal(3).

This was originally done in 86476906 but it missed some use
of 'signal' in prototypes in headers where it didn't cause
warnings. Later the prototypes were moved around and the
warnings came back.

This also cleans up some cases in where stdlib.h was used
but shouldn't be required.
Add extern "C" protection to opus_multistream.h.

Unlike the other headers, opus_multistream.h didn't declare
itself to be C code, causing confusing errors when the caller
tries to use the functions from C++.
Fix opus-uninstalled.pc.

With these changes, opus-tools can actually build using it.
Fixes some cases where MIN/MAX macros result in duplicated function calls

Also enforces an upper bound of 510 kb/s even for frames that are
smaller than 20 ms. This reduces waste for high bitrate VBR.
Advertise the static library for uninstalled builds.

It's less surprising for people using the -uninstalled
pkg-config file if we advertise the static library rather
than the shared build. That way the executables work without
having to hack the same location into LD_LIBRARY_PATH, and
the resulting binaries are easier to distribute.

For this to actually work with opus-tools, the -fPIE had
to be turned off, as it was in 1d128b4d5c6f. Support
for static PIE builds would be restored if we compiled
libopus.a with -fPIC.

Also remove the private header locations. These are no
longer required to declare any of the public api.
Fix for building mingw32 apps.
Seems like using dllimport on Windows wasn't useful

This was a problem for static builds
Avoid an inconsequential memory leak in tests/test_opus_encode.c.
 Avoid an inconsequential memory leak in tests/test_opus_decode.c
modified the Visual Studio 2010 projects and solution file to include a x64 configuration. modified the output folders such that the architecture is included in the path (so you get Release64, Debug32, etc.) so you can have all build types in one tree.
Update headers to cause warnings on unused returns and null args.

In places where an ignored return or a null-arg is a sure indication
of a bug add the GCC warning attributes. The null arg annotation
is not enable for Opus itself because it will cause the compiler
to optimize out some null checks. I don't trust our callers
quite that much.
Fix doxygen docs wrt OPUS_WARN_UNUSED_RESULT and OPUS_ARG_NONNULL.

Also get the subname rigtht.