Remove duplication of memory access functions between jpeg and musyx modules.
Rewrite audio ucode identification using the new RDRAM access primitives.
Use dram access primitives for remaining cases in main.c
Use dram access primitives in alist.c
Prefer memory access primitives over struct OSTask_t.

Structure fields alignment is compiler dependent and therefore can be fragile.
We replace all occurences of OSTask_t structure by memory access primitives.