glsl/glcpp: Drop the HASH_ prefix from token names like HASH_IF

glsl/glcpp: Drop the HASH_ prefix from token names like HASH_IF

Previously, we had a single token for "#if" but now that we have two separate
tokens, it looks much better to see:

	HASH_TOKEN IF

than:

	HASH_TOKEN HASH_IF

(Note, that for the same reason we use HASH_TOKEN instead of HASH, we also use
DEFINE_TOKEN instead of DEFINE to avoid a conflict with the <DEFINE> start
condition in the lexer.)

There should be no behavioral change from this commit.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>