compiled with stack protector.

Use libssp_nonshared library to pull __stack_chk_fail_local symbol into
each library that needs it instead of pulling it from libc. GCC
generates local calls to this function which result in absolute
relocations put into position-independent code segment, making dynamic
loader do extra work every time given shared library is being relocated
and making affected text pages non-shareable.

Reviewed by:        kib
Approved by:        re (kib)

Approved by: re (impliciti, by approving previos check-in)

Use libssp_nonshared library to pull __stack_chk_fail_local symbol into
each library that needs it instead of pulling it from libc. GCC generates
local calls to this function which result in absolute relocations put into
position-independent code segment, making dynamic loader do extra work everys
time given shared library is being relocated and making affected text pages
non-shareable.

Reviewed by:        kib
Approved by:        re (kensmith)

Also:
        Switch FreeBSD to use libgcc_s.so.1.

        Use dl_iterate_phdr to locate shared objects' exception frame
        info instead of depending on older register_frame_info machinery.
        This allows us to avoid depending on libgcc_s.so.1 in binaries
        that do not use exception handling directly. As an additional
        benefit it breaks circular libc <=> libgcc_s.so.1 dependency too.

        Build newly added libgomp.so.1 library, the runtime support
        bits for OpenMP.

        Build LGPLed libssp library. Our libc provides our own
        BSD-licensed SSP callbacks implementation, so this library
        is only built to benefit applications that have hadcoded
        knowledge of libssp.so and libssp_nonshared.a. When linked
        in from command line, these libraries override libc
        implementation.