style: formatting clean up

* data/skeletons/d.m4, examples/d/calc.y, src/output.c,
* src/parse-gram.y:
No tab, no trailing spaces.
Reported by syntax-check.

src/parse-gram.y

@@ -462,7 +462,7 @@ tag:
 `-----------------------*/
 
 // A non empty list of possibly tagged symbols for %nterm.
-// 
+//
 // Can easily be defined like symbol_decls but restricted to ID, but
 // using token_decls allows to reudce the number of rules, and also to
 // make nicer error messages on "%nterm 'a'" or '%nterm FOO "foo"'.