Move all the code in a single .h file

It calls strdup on its parameters internally.

decoder takes the size of encoded buffer and returns number of samples
encoder takes the maximum size of output buffer and returns compressed size
(it assumes we will encode only one frame at a time)

fix a use after free

Try to avoid confusion between size in bytes and number of samples
Use statically allocated buffers for decoders / encoders / filters / resamplers

We assume we won't be processing more than 20ms of audio mono at 44.1kHz

This reverts commit f0a7fe36.

That way we're guaranteed that it is safe to delete it after.

don't call methods on deleted objects!

Also the memory pool for the SDP must be deallocated after we've destroyed
the SDP.

Resolved Conflicts:
	sflphone-common/src/audio/algorithm.h
	sflphone-common/src/audio/audiortp/AudioRtpRecordHandler.cpp

This lead to a dead-lock in its destructor. Instead, AudioRtpFactory
must delete it.

also fix wrong assertion about the final number of samples

The GUI lets user choose .ul (ULAW) or .au files (GSM)
However RawFile class assumes ULAW only so we reject GSM files

Also resample the whole sample buffer given