glsl/glcpp: Test that macro parameters substitute immediately after periods

At one point while rewriting the lexing rule for pre-processing numbers, I
made it a bit too aggressive and within a replacement list sucked up a
parameter name that appeared immediately after a period. This caused the
parameter name to be unreplaced when the macro was expanded.

It was in some piglit tests that I originally found this issue. Here, I'm
adding a test to "make check" to ensure that this behavior remains correct.

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

src/glsl/glcpp/tests/137-expand-macro-after-period.c

@@ -0,0 +1,4 @@
+#define FIELD(x) foo.x
+#define FIELD_OF(s, x) s.x
+FIELD(bar)
+FIELD_OF(foo, bar)

src/glsl/glcpp/tests/137-expand-macro-after-period.c.expected

@@ -0,0 +1,4 @@
+
+
+foo.bar
+foo.bar