make the RAWCPP test a little more sensible.

remove bogus [ ] in macro for leading underscore test.

Fix the sed string for the gcc check, it was referring to sub-regexps
that didn't exist.

Drop egcs support for gcc test

use * instead of ?, since some seds don't recognise ?, and some also
don't recognise the alternative \{0,1\}. sigh.

remove spurious comma.

Moved feature tests from configure.in to aclocal.m4 and macroified them

fptools specific autoconf macros