Dont eat newlines on parametrized macro invocations (RhBug:1045723)

- Makes the testcase from commit f082b5baa4
  succeed. While the old behavior is non-sensical and most likely entirely
  unintentional, we're changing a very long-standing behavior here (tested
  back to rpm 4.4.x and almost certainly much much older than that) so
  its entirely possible people are actually relying on the old
  behavior. Lets see what breaks...

rpmio/macro.c

@@ -764,7 +764,7 @@ grabArgs(MacroBuf mb, const rpmMacroEntry me, const char * se,
 
 exit:
     argvFree(argv);
-    return *lastc ? lastc + 1 : lastc; 
+    return (*lastc == '\0' || *lastc == '\n') ? lastc : lastc + 1;
 }
 
 /**