Fixes bug 45747. Proxy auth does not handle multiple Proxy-Authenticate

headers.  Causes problems with MS proxy server II.  Patch supplied by
Brandon_Stewart@circuitcity.com.  r=darin, sr=mscott.

netwerk/protocol/http/src/nsHTTPHeaderArray.cpp

@@ -157,7 +157,8 @@ nsresult nsHTTPHeaderArray::SetHeader(nsIAtom* aHeader,
   //
   else if (IsHeaderMultiple(aHeader)) {
     if (nsHTTPAtoms::Set_Cookie == aHeader ||
-            nsHTTPAtoms::WWW_Authenticate == aHeader) {
+        nsHTTPAtoms::WWW_Authenticate == aHeader ||
+        nsHTTPAtoms::Proxy_Authenticate == aHeader) {
         // special case these headers and use a newline
         // delimiter to delimit the cookies from one another
         // we can't use the standard comma because there