Disable some sanitizer checks without PEDANTIC

Code without PEDANTIC has intentional "undefined" behaviour. To get best
coverage for both PEDANTIC and non-PEDANTIC codepaths, run the sanitizer
builds in two different configurations:
1) Without PEDANTIC but with alignment checks disabled.
2) With PEDANTIC.

To not overload Travis too much, run one build with clang and the other
with gcc (chosen at random).

Also remove a micro-optimization in CAST code to be able to
-fsanitize=shift. Whether shift sanitization is meaningful for crypto or
an obstacle is debatable but since this appears to be the only offender,
we might as well keep the check for now.

Reviewed-by: Richard Levitte <levitte@openssl.org>