glsl: Replace most default cases in switches on GLSL type

glsl: Replace most default cases in switches on GLSL type

This makes it easier to find switch-statements that need to be updated
after a new GLSL_TYPE_* is added because the compiler will generate a
warning.

Switch-statements that only had a small number of cases (e.g.,
everything in ir_constant_expression.cpp) were not modified.  I may
regret that decision when we eventually add support for doubles.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Carl Worth <cworth@cworth.org>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>