Add rudimentary support and stubs for libthr and libc_r on alpha, amd64,

Add rudimentary support and stubs for libthr and libc_r on alpha, amd64,
i386, ia64 and sparc64. Add stubs for alpha, amd64, ia64 and sparc64 for
libpthread.

Restructure the source files to avoid unnecessary use of subdirectories
that also force us to use non-portable compilation flags to deal with
the uncommon compilation requirements (building archive libraries for
linkage into a shared library).

The libpthread support has been copied from the original local and
cleaned-up to make them WARNS=2 clean.
that also force us to use non-portable compilation flags to deal with
the uncommon compilation requirements (building archive libraries for
linkage into a shared library).

The libpthread support has been copied from the original local and
cleaned-up to make them WARNS=2 clean.

Tested on: amd64, i386, ia64