glsl: Add flex options to eliminate the default rule

We've had bugs in the past where we have been inadvertently matching the
default rule.

Just as we did in the pre-processor in the previous commit, we can use:

	%option warn nodefault

in the compiler to instruct flex to not generate the default rule, and
further to warn if our set of rules could let any characters go unmatched.

With this warning active, flex actually warns that the catch-all rule we
recently added to the compiler could never be matched. Since that is all
safely determined at compile time now, we can safely drop this run-time
compiler error message, (as we do in this commit).

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>

src/glsl/glsl_lexer.ll

@@ -152,6 +152,7 @@ literal_integer(char *text, int len, struct _mesa_glsl_parse_state *state,
 %option never-interactive
 %option prefix="_mesa_glsl_lexer_"
 %option extra-type="struct _mesa_glsl_parse_state *"
+%option warn nodefault
 
 	/* Note: When adding any start conditions to this list, you must also
 	 * update the "Internal compiler error" catch-all rule near the end of
@@ -559,16 +560,6 @@ subroutine	KEYWORD(0, 300, 0, 0, SUBROUTINE);
 
 .			{ return yytext[0]; }
 
-	/* This is a catch-all to avoid the annoying default flex action which
-	 * matches any character and prints it. If any input ever matches this
-	 * rule, then we have made a mistake above and need to fix one or more
-	 * of the preceding patterns to match that input. */
-<PP,PRAGMA>. {
-	_mesa_glsl_error(yylloc, yyextra,
-                         "Internal compiler error: Unexpected character: %s", yytext);
-}
-
-
 %%
 
 int