Simplify calloc implementation.

To make future improvements of allocator simpler we could for now calloc
just call malloc and memset. With that we could omit a changes that
would duplicate malloc changes anyway.
PowerPC: Update powerpc-fpu ULPs.
Add a new "Inter-Process Communication" chapter.

This patch adds a new "Inter-Process Communication"
chapter to cover the sem*, msg*, and shm* functions.
Initially we document only the sem* function signatures
and their safety notes.