dvtm 0.13

Updated dvtm to 0.13. Had to do a little inreplacing to work around OSX selectively removing SIGWINCH/VLNEXT in signal.h/termios.h when -D_POSIX_C_SOURCE is defined. Added a simple test.
dvtm's own testsuite.sh involves testing the ancillary copymode functionality and requires wget, vis, and vi (see: http://repo.or.cz/w/dvtm.git/blob/HEAD:/testsuite.sh). For main program features it just tests dvtm -v. Is there a way to require wget (I assume vis & vi are available) for the test recipe?