glsl/glcpp: Fix to emit spaces following directives

The glcpp lexer and parser use the space_tokens state bit to avoid emitting
tokens for spaces while parsing a directive. Previously, this bit was only
being set again by the first non-space token following a directive.

This led to a bug where a space, (or a comment that should emit a space),
immediately following a directive, (optionally searated by newlines), would be
omitted from the output.

Here we fix the bug by also setting the space_tokens bit whenever we lex a
newline in the standard start conditions.

src/glsl/glcpp/glcpp-lex.l

@@ -355,6 +355,7 @@ HEXADECIMAL_INTEGER	0[xX][0-9a-fA-F]+[uU]?
 	if (parser->commented_newlines) {
 		BEGIN NEWLINE_CATCHUP;
 	}
+	yyextra->space_tokens = 1;
 	yyextra->lexing_directive = 0;
 	yylineno++;
 	yycolumn = 0;

src/glsl/glcpp/tests/125-es-short-circuit-undefined.c.expected

@@ -8,6 +8,7 @@
 
 #version 300 es
 
+ 
 
 
 
@@ -15,8 +16,7 @@
 
 
 
-
-
+ 
 
 Success