macosx: increase maximum number of messages for the messages panel
macosx: increase maximum number of messages for the messages panel

This is needed to a complete log as some modules like mkv are very
verbose. The actual size is not so critical anymore as messages
are only arriving if the panel is open.

xkfz007/vlc,krichter722/vlc,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,krichter722/vlc,jomanmuk/vlc-2.2,shyamalschandra/vlc,shyamalschandra/vlc,krichter722/vlc,vlc-mirror/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.2,krichter722/vlc,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,xkfz007/vlc,krichter722/vlc,xkfz007/vlc,jomanmuk/vlc-2.2,krichter722/vlc,xkfz007/vlc,xkfz007/vlc,vlc-mirror/vlc,vlc-mirror/vlc,shyamalschandra/vlc,vlc-mirror/vlc,vlc-mirror/vlc,xkfz007/vlc,xkfz007/vlc,vlc-mirror/vlc,shyamalschandra/vlc,krichter722/vlc,vlc-mirror/vlc,shyamalschandra/vlc,shyamalschandra/vlc