updated for version 7.4.305
Problem:    Making 'ttymouse' empty after the xterm version was requested
	    causes problems. (Elijah Griffin)
Solution:   Do not check for DEC mouse sequences when the xterm version was
	    requested.  Also don't request the xterm version when DEC mouse
	    was enabled.
Added tag v7-4-305 for changeset 63e7cc62402d