vax.h (CASE_DROPS_THROUGH): Don't define.

vax.h (CASE_DROPS_THROUGH): Don't define.

	rtl-optimization/12863
        * config/vax/vax.h (CASE_DROPS_THROUGH): Don't define.
        * config/vax/vax.md (casesi): Emit a test-and-branch to make sure
        that the case is in range, to make sure the casesi insn is always
        in range and never falls through.
        (casesi1): Add comment to explain why casesi never falls through.
        Remove the unnamed special case casesi pattern.

Co-Authored-By: John David Anglin <dave.anglin@nrc-cnrc.gc.ca>
From-SVN: r92661