[SRC_C] Improve implementation of lib/posix sections

LIB:

• Improved control on some arguments about the consistency of parameters passed as reference (check of NULL pointer).
• Introduced additional functions.
• Increased from 8 to 10 bytes. This is for eventually an additional path version field.

POSIX:

• Add/Change command line arguments.
• Management of -c and -l options was missed.
• Add logic used to establish the conf file to use.
• Add read and write function for block devices.
• All tasks the tool is designed for have been implemented.