There were two problems before that this fixes.  One was that the
check for the compiler error return code preceded the determination
of the compiler and its options.  The other was that the checks
for compiler and library characteristics could be fooled if the
error options were set to reject K&R-style C.  configure now aborts
if the compiler produces a hard error on K&R-style C.

In addition, aborts of configure are now consistent, and remove
any temporary files.