Expand parametric macro arguments before processing (#127, RhBug:1397209)

This too is quite a fundamental change for macros: up to now, arguments
to parametric macros have not been expanded. It doesn't sound so bad
until you consider something like the case in RhBug:1397209:

        %global rev 133
        ...
        %setup %{?rev:-c}
        %autosetup %{?rev:-c}

One would expect %setup and %autosetup behave the same when you replace
one with the other, but no.  %setup gets "called" with -c, %autosetup
does not. Instead %autosetup receives a completely useless, literal
"%{?rev:-c}" as its argument.  That's just brain-meltingly non-sensical.

This certainly has the potential to break advanced macro constructs,
but OTOH what breaks might well be only written that way in order to
work around the former behavior.

There are some funny subtleties involved as the argument expansion
must occur in the callers scope, ie before we create any of the
automatic macros. For example, Fedora's font packages break if only
this or the macro scope visibility enforcement is applied but start
working again once both are present.

rpmio/macro.c

@@ -675,9 +675,10 @@ grabArgs(MacroBuf mb, const rpmMacroEntry me, const char * se,
     argvAdd(&argv, me->name);
     if (lastc) {
 	ARGV_t av = NULL;
-	char *s = xcalloc((lastc-se)+1, sizeof(*s));
-	memcpy(s, se, (lastc-se));
+	char *s = NULL;
 
+	/* Expand possible macros in arguments */
+	expandThis(mb, se, lastc-se, &s);
 	argvSplit(&av, s, " \t");
 	argvAppend(&argv, av);