While 325b3042edd6 fixed it on MINIX, it broke it on systems
that output the word "version" on several lines with "cc -v".
The fix is to only consider "clang version" or "LLVM version"
as clang version, but this time only using sed(1).

As per POSIX, basic regular expressions have no alternations, and the
interpretation of the "\|" construct is undefined.  At least on MINIX
and Solaris grep interprets "\|" as literal "|", and not as an alternation
as GNU grep does.  Removed such constructs introduced in f1daa0356a1d.
This fixes clang detection on MINIX.

Oracle Developer Studio 12.5 introduced GCC-compatible __sync builtins.
Unfortunately, these builtins are neither GCC-compatible (they generate
warnings when used with volatile), nor working (unexpectedly fail on
unpredictable combinations of code layout and compiler flags).  As such,
the gcc builtin atomic operations configure test explicitly disabled when
compiling with Sun C.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

This reduces the number of moving parts in ABI compatibility checks.
Additionally, it also allows to use OpenSSL in FIPS mode while still
using md5 for non-security tasks.

Now GCC 6 and onwards will use -Wno-unused-parameter.