exception propagation support not enabled in libstdc++ 4.4 on {armeabi,hppa,sparc}-linux

[Matthias Klose]

Noticed that some symbols introduced for the exception propagation support are
missing in libstdc++.so.6 on arm-linux-gnueabi, hppa-linux-gnu and
sparc-linux-gnu (no results for mips*-linux yet). The libstdc++ configure check
GLIBCXX_ENABLE_ATOMIC_BUILTINS fails, because three of the five __sync_*
functions are still seen in the asm code (not seen: __sync_lock_release and
__sync_synchronise).

libgcc.a has all of the __sync_* functions defined, and the configure (link)
tests in libgomp and libgfortran do succeed. Unsure what I'm doing wrong with
the libstdc++ configury. Is this seen on other linux builds for these targets as
well?

  Matthias