glcpp/tests: Add test for multiline #if

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/glsl/glcpp/tests/106-multiline-hash-if.c

@@ -0,0 +1,6 @@
+#define X(x) x
+#if X(		\
+	1	\
+     )
+int foo();
+#endif

src/glsl/glcpp/tests/106-multiline-hash-if.c.expected

@@ -0,0 +1,7 @@
+
+
+
+
+int foo();
+
+