glcpp: Support #elif(expression) with no intervening space.

And add test cases to ensure that this works
	- 110 verifies that glcpp rejects #elif<digits> which glcpp
	  previously accepted.
	- 111 verifies that glcpp accepts #if followed immediately by
	  (, +, -, !, or ~.
	- 112 does the same as 111 but for #elif.

See 17f9beb6 for #if change.
Reviewed-by: Carl Worth <cworth@cworth.org>

src/glsl/glcpp/tests/111-no-space-operator-after-hash-if.c.expected

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