Fix new (MSVC) warnings

which were result of QWK_NEWLINE redef to make cppcheck happy

src/sbbs3/msgtoqwk.cpp

@@ -246,7 +246,7 @@ int sbbs_t::msgtoqwk(smbmsg_t* msg, FILE *qwk_fp, int mode, smb_t* smb
 	if(!buf)
 		return -2;
 
-	char qwk_newline = QWK_NEWLINE;
+	uchar qwk_newline = QWK_NEWLINE;
 	if(smb_msg_is_utf8(msg) || (msg->hdr.auxattr & MSG_HFIELDS_UTF8)) {
 		if(mode&QM_UTF8)
 			qwk_newline = '\n';

src/sbbs3/qwktomsg.cpp

@@ -314,7 +314,7 @@ bool sbbs_t::qwk_import_msg(FILE *qwk_fp, char *hdrblk, uint blocks
 
 	kludges=strListInit();
 
-	char qwk_newline = QWK_NEWLINE;
+	uchar qwk_newline = QWK_NEWLINE;
 	if(msg->hdr.auxattr & MSG_HFIELDS_UTF8)
 		qwk_newline = '\n';