Don't emit whitespace when stringifying TOKEN_WHITE.

Other aspects of the preprocessor already skip whitespace leading up to a token. The only situation in which a TOKEN_WHITE can
exist as part of the token stream during stringification, is when the whitespace is trailing after a token. This is situation is
really only possible in the context of a macro argument. This behaviour is inconsistent.

Consider the following
FOO( space_before)
FOO(space_after )

The former will reduce to "space_before" since the preprocessor will skip whitespace leading up to the token `space_before', while
the latter will reduce to "space_after ".

The C preprocessor doesn't preserve whitespace, so we won't either. This doesn't break any existing code.

ftepp.c

@@ -703,9 +703,9 @@ static void ftepp_stringify_token(ftepp_t *ftepp, pptoken *token)
                 ++ch;
             }
             break;
-        case TOKEN_WHITE:
+        /*case TOKEN_WHITE:
             ftepp_out(ftepp, " ", false);
-            break;
+            break;*/
         case TOKEN_EOL:
             ftepp_out(ftepp, "\\n", false);
             break;