values implementation
Merge branch 'dev' of https://github.com/mickael-menu/libpirt into dev

Conflicts:
	Makefile
	include/commit.h
	include/pi_thread.h
	include/value.h
	src/commit.c
	src/pi_thread.c
	tests/channel_test.c
implemented some primitives on values
a test script in runtime_test.c
new value functions - invariant todo
Merge branch 'dev' of https://github.com/mickael-menu/libpirt into dev
minor corrections and adding some value functions
correction on value kind test
minor corrections
Refactor values and various corrections
WORD SIZE definition in runtime.c and compare_values in value.c
adding an evalFunction getter for commit and declaring the type PICC_EvalFunction as a pointer
small modifications to value.c
merging
I'm adding some signatures to make the C code generated by pcc able to compile with gcc.
I've implemented some of this function, but most of them are just empty and waiting to be completed ^^
Most of the knownset was done by Maxence.
I've write the iterator part and rewrite the for loops in channel.c so they use it.
Corrections in known sets
Delete knownset_tree|list.c
Add a new Makefile rules for auto-inclusion of .c
Correct the static initialization in value_repr.h
Merge of knownset / set_functions + GC