Catching SEGVs with __try/__except is MSVC only, not general C++

Catching SEGVs with __try/__except is MSVC only, not general C++

__try/__except is an MSVC extension to C++ *and* C, and is orthogonal to
"regular" C++ exception handling. As there's no way to catch a SEGV with
C++ exceptions (certainly not portably), and __try/__except is available in C,
there's nothing to be gained from using C++ exceptions, and hence making the
code require a C++ compiler. Hence remove the logic from Makefile.PL to force
compilation with a C++ compiler, which didn't even work well on "both" kinds of
OS, as it assumed that the C compiler was named *exactly* qr/\Ag?cc\z/, and
that the analogous C++ compiler was available and named g++.

[Which isn't true when it's named 'ccache gcc', 'gcc-mp-4.6' etc, or when cc
isn't gcc]