Move -Wswitch from -Wmost to -Wall, consitent with GCC.

This is a relatively noisy warning for a codebase not explicitly designed for
it (effectively enforcing a stylistic constraint about the use of defaults
in switches over enums) & there's nothing Clang does to clean up the noise
when compared to GCC's implementation so the same decision seems suitable.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150230 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed