Correct gcc version check for __cxa_begin_catch() declaration with or without throw().
Correct gcc version check for __cxa_begin_catch() declaration with or
without throw().

The version check was incorrectly implemented, and did not work for gcc
>= 5.0.  Additionally, __cxa_begin_catch() is first implicitly declared
with throw() by gcc 4.4.0 and higher.

cemeyer/libcxxrt,vegard/libcxxrt,cemeyer/libcxxrt,vegard/libcxxrt,cemeyer/libcxxrt,vegard/libcxxrt