[Moto4lin-main] Fixes (mainly) for p2k_FSAC_read

[Mattia B. <mat...@li...>]

  Hi,
the patch below fixes p2k_FSAC_read to actually work (before
it was using an uninitialized value for size).

  While at it, I fixed all warnings that are emitted with -O3 -Wall -W.
Most of the warnings are harmless, bus some might have fixed some latent
bugs.

  Are there any plans to release a new version of libp2kmoto?  The last
released version is very old.

Best regards,
Mattia