glcpp: Fix support for nested #ifdef and nested #ifndef

Previously, if the outer #ifdef/#ifndef evaluated to false, the inner
directive would not be parsed correctly, (the identifier as the subject
of the #ifdef/#ifndef would inadvertently be skipped along with the other
content correctly being skipped).

We fix this by setting the lexing_if state in each case here.

We also add a new test to the test suite to ensure that this case is tested.

src/glsl/glcpp/glcpp-lex.l

@@ -90,16 +90,18 @@ HEXADECIMAL_INTEGER	0[xX][0-9a-fA-F]+[uU]?
 }
 
 {HASH}ifdef/.*\n {
+	yyextra->lexing_if = 1;
 	yyextra->space_tokens = 0;
 	return HASH_IFDEF;
 }
 
 {HASH}ifndef/.*\n {
+	yyextra->lexing_if = 1;
 	yyextra->space_tokens = 0;
 	return HASH_IFNDEF;
 }
 
-{HASH}if{HSPACE}*/[^_a-zA-Z0-9].*\n {
+{HASH}if/[^_a-zA-Z0-9].*\n {
 	yyextra->lexing_if = 1;
 	yyextra->space_tokens = 0;
 	return HASH_IF;
@@ -122,7 +124,7 @@ HEXADECIMAL_INTEGER	0[xX][0-9a-fA-F]+[uU]?
 }
 
 	/* When skipping (due to an #if 0 or similar) consume anything
-	 * up to a newline. We do this less priroty than any
+	 * up to a newline. We do this with less priority than any
 	 * #if-related directive (#if, #elif, #else, #endif), but with
 	 * more priority than any other directive or token to avoid
 	 * any side-effects from skipped content.

src/glsl/glcpp/tests/067-nested-ifdef-ifndef.c

@@ -0,0 +1,40 @@
+#define D1
+#define D2
+
+#define result success
+
+#ifdef U1
+#ifdef U2
+#undef result
+#define result failure
+#endif
+#endif
+result
+
+#ifndef D1
+#ifndef D2
+#undef result
+#define result failure
+#endif
+#endif
+result
+
+#undef result
+#define result failure
+#ifdef D1
+#ifdef D2
+#undef result
+#define result success
+#endif
+#endif
+result
+
+#undef result
+#define result failure
+#ifndef U1
+#ifndef U2
+#undef result
+#define result success
+#endif
+#endif
+result

src/glsl/glcpp/tests/067-nested-ifdef-ifndef.c.expected

@@ -0,0 +1,41 @@
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+success
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+success
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+success
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+success
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