configure and gcctestsuite.sh shell scripts contains bashisms although being
bourne shell script. This patch fixes the following bashisms:
* Use of $RANDOM variable (replaced by reading in /dev/urandom)
* Use == in tests instead of just =
* Use $[] for arithmetic computation istead of $(())
(Because GNU's alloca.h unconditionally #undef's alloca)
Also, remove gcc specific sections in headers. and
instead change tests such that gcc does not use them.
