fix build warnings, patch by Aleksey Nogin, r=ducarroz, sr=bienvenu 59673

mailnews/local/src/nsParseMailbox.cpp

@@ -779,7 +779,7 @@ NS_IMETHODIMP nsParseMailMessageState::GetHeaders(char ** pHeaders)
   NS_ENSURE_ARG_POINTER(pHeaders);
   nsCString crlfHeaders;
   char *curHeader = m_headers.GetBuffer();
-  for (PRInt32 headerPos = 0; headerPos < m_headers.GetBufferPos();)
+  for (PRUint32 headerPos = 0; headerPos < m_headers.GetBufferPos();)
   {
     crlfHeaders.Append(curHeader);
     crlfHeaders.Append(CRLF);

mailnews/local/src/nsPop3Sink.cpp

@@ -476,7 +476,7 @@ nsPop3Sink::IncorporateComplete(nsIMsgWindow *msgWindow)
 {
   if (m_buildMessageUri && m_baseMessageUri)
   {
-      PRUint32 msgKey = -1;
+      PRUint32 msgKey;
       m_newMailParser->GetEnvelopePos(&msgKey);
       m_messageUri.SetLength(0);
       nsBuildLocalMessageURI(m_baseMessageUri, msgKey, m_messageUri);

mailnews/mime/emitters/src/nsMimeHtmlEmitter.cpp

@@ -207,7 +207,7 @@ NS_IMETHODIMP nsMimeHtmlDisplayEmitter::WriteHTMLHeaders()
       headerNames[numHeadersAdded] = headerInfo->name;
 
       if (nsCRT::strcasecmp("Date", headerInfo->name) == 0)
-        nsresult rv = GenerateDateString(headerInfo->value, &headerValues[numHeadersAdded]);
+        rv = GenerateDateString(headerInfo->value, &headerValues[numHeadersAdded]);
       else
       {
         // optimization: if we aren't in view all header view mode, we only show a small set of the total # of headers.