glsl: Properly lex extra tokens when handling # directives.

Without this, in the <PP> state, we would hit Flex's default rule, which
prints tokens to stdout, rather than returning them as tokens. (Or, after the
previous commit, we would hit the new catch-all rule and generate an internal
compiler error.)

With this commit in place, we generate the desired syntax error.

This manifested as a weird bug where shaders with semicolons after
extension directives, such as:

   #extension GL_foo_bar : enable;

would print semicolons to the screen, but otherwise compile just fine
(even though this is illegal).

Fixes Piglit's extension-semicolon.frag test.

This also fixes the following Khronos GLES3 conformance tests, (and for real
this time):

	invalid_char_in_name_vertex
	invalid_char_in_name_fragment

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Carl Worth <cworth@cworth.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

src/glsl/glsl_lexer.ll

@@ -239,6 +239,7 @@ HASH		^{SPC}#{SPC}
 				    return INTCONSTANT;
 				}
 <PP>\n				{ BEGIN 0; yylineno++; yycolumn = 0; return EOL; }
+<PP>.				{ return yytext[0]; }
 
 \n		{ yylineno++; yycolumn = 0; }