Bug 1344629 - Part 4: Cleanup: make string tuples not think in terms of "substring". r=dbaron

In the next patch, tuples will work on nsTStringRepr rather than nsTSubstring, so the notions of TO_SUBSTRING and substring_type are not quite right.

MozReview-Commit-ID: LpUwmGQAWVO

xpcom/string/nsSubstringTuple.cpp

@@ -6,9 +6,6 @@
 
 #include "nsSubstringTuple.h"
 
-// convert fragment to |const substring_type&|
-#define TO_SUBSTRING(_v) (*(_v))
-
 // define nsSubstringTuple
 #include "string-template-def-unichar.h"
 #include "nsTSubstringTuple.cpp"