MDL-50113 message: responsive and long name fixups

Addresses responsive inconsistency on Firefox, also fixes display
of names which are long and don't have whitespace to break on.

theme/bootstrapbase/less/moodle/message.less

@@ -11,6 +11,7 @@
     font-size: 1em;
     font-weight: bold;
     clear: both;
+    word-wrap: break-word;
 }
 .message .author {
     font-weight: bold;
@@ -37,6 +38,9 @@
 #page-message-send td.fixeditor {
     text-align: center;
 }
+.message {
+    overflow: hidden;
+}
 .message .note {
     padding: 10px;
 }