progress towards fixing 123041 - stop making copies of entities names and values as we retrieve them out of various entity tables

also, a few uses of NS_LITERAL_STRING, removal of long-since-unused nsHTMLContentSinkStream
r/sr=sfraser, sr=jag, r=harishd

parser/htmlparser/src/nsViewSourceHTML.cpp

@@ -882,7 +882,7 @@ nsresult CViewSourceHTML::WriteAttributes(PRInt32 attrCount) {
           const nsAReadableString& theKey=theAttrToken->GetKey();
 
           result=WriteTag(mKey,theKey,0,PR_FALSE);
-          const nsString& theValue=theAttrToken->GetValue();
+          const nsAString& theValue=theAttrToken->GetValue();
 
           if((0<theValue.Length()) || (theAttrToken->mHasEqualWithoutValue)){
             result=WriteTag(mValue,theValue,0,PR_FALSE);