Eat whitespace while in the PP state

glsl_lexer.lpp

@@ -62,6 +62,7 @@
 ^[ \t]*#[ \t]*line		{ BEGIN PP; return LINE; }
 ^[ \t]*#[ \t]*pragma		{ BEGIN PP; return PRAGMA; }
 <PP>\/\/[^\n]*			{ }
+<PP>[ \t\r]*			{ }
 <PP>:				return COLON;
 <PP>[_a-zA-Z][_a-zA-Z0-9]*	{
 				   yylval->identifier = strdup(yytext);