Full list of changes:

Added support for 256 color xterms.
Added encode_ansi() to generate a string with ANSI display codes.
Added test() for backward compatiblity with version 4.0.
Added strcmpattr(), like strcmp() but also compares display attributes.
In commands that match macros (/list, /purge, /save), a color attribute will
match only the same color attribute, not just any color attribute.
Added -n option to /listsockets to print host and port in numeric form.
%Pn, %L, and %R subs are now case sensitive, to reduce collisions with regular
variables.
CONNECT hook includes SSL cipher name.
Added -f (foreground) and -b (background) options to /world; documented -x
(SSL) option.
Status bar changes:
Status bar can be multiple rows, determined by %status_height.
/status_{add,edit,rm} commands take an -r option to specify which row.
Added /status_defaults to restore default status bar fields; use of
%status_field_defaults is deprecated.
Added "/status_save <name>" and "/status_restore <name>" to save and
restore a named set of status fields.
Fixed: "/status_add -x name:width:attr" failed to detect existing field
with name if its width or attr were different.
Fixed: status_attr_{int,var}_* variables sometimes had no effect. (50b5)
Fixed: any attempt to set %status_pad in .tfrc failed if %visual had not
yet been explicitly set (also, in a RESIZE hook caused by a terminal
resize while in /suspend or /sh, but that's much less common). (50a13)
Other screen display changes:
Changing %wrappunct immediately rewraps everything on screen.
Eliminated extra screen redraw when the terminal is resized.
Fixed: under some conditions, rewrapping screen could cause entire
scrollback buffer to be redrawn, instead of just a screenful. (If
%more was on, this acted like a jump to the beginning of the buffer.)
Fixed: did not send new terminal size to server after resizing the
terminal
in nonvisual mode.
Workaround for a window resize bug in Konsole.
Keyboard changes:
Workaround for incomplete linux console terminfo entry which was
preventing
%keypad from working.
Added friendlier message for using undefined named keys.
Improved documentation for numeric keypad, including instructions for
using it with some specific terminal emulators. (See "/help keypad".)
Added missing names for numeric keypad keys: key_nkpTab key_nkpEnt
key_nkp* key_nkp+ key_nkp, key_nkp- key_nkp. key_nkp/ key_nkp=
Added default keybindings for shift-tab, sun function keys, and
vt220 function keys F13 - F20.
Fixed incorrect keybindings for bottom two rows of numeric keypad in some
environments.
Installation changes:
./configure now honors options --exec-prefix, --bindir, --datadir,
--program-prefix, --program-suffix, and --program-transform-name.
./configure --enable-version does not automatically --enable-symlink.
Installation directory for tf-lib now defaults to PREFIX/share instead of
PREFIX/lib (configurable with --datadir).
Fixed ./configure --enable-mailcheck=DIR.
ftime() now returns an empty string instead of an incorrect string if the time
is out of range (in addition to printing an error message).
Time period values of 60s or larger are printed in h:mm[:ss.u] format. This
applies to %alert_time, %maildelay, %prompt_wait, %ptime, idle(), sidle(),
and values derived from them (but not time() and mktime(), which are
absolute time values).
The CONFAIL and CONNETFAIL hooks did not previously behave as documented. The
CONNETFAIL hook has been removed; the new ICONFAIL hook is called for a
connection failure if there are more possible addresses to try, and the
CONFAIL hook is called for a connection failure on the last address. (If
you had worked around the buggy behavior by duplicating CONFAIL and
CONNETFAIL hooks, you will probably want to go back to using the CONFAIL
hook only.)
Improved error checking for /repeat arguments.
Fixed spurious error for "/break" without arguments at end of macro body.
Fixed: a macro with no other statements outside of an "/if (expr)" statement
was incorrectly treated as an error, causing any macro that called it
to abort.
Fixed: "/set var " (with trailing space) was setting var to blank instead
of printing its value.
Fixed: /runtime incorrectly evaluated its return value.
Fixed: new -= operator added instead of subtracted.
Fixed crash if left side of new += -= *= /= operators was not assignable.
Fixed crash in strip_attr(). (50b5)
Fixed crash in /list -P.
Fixed class of crashes involving certain generated empty strings in macros:
- attribute strings in echo(), substitute(), and decode_attr()
- macro names
- expression operands
- etc.
Will not crash if a bug in tf or library code supplies an invalid string in
an error message.
Strengthened check for TERMCAP corruption by broken *csh.
Fixed moresize() and morepaused() with virtscreen=off (undocumented).

^o^