This patch is to fix Bug 16762 - GDB doesn't update display size when host
terminal resize, and it inadvertently fixes Bug 15958 - readline modifies
env (LINES+COLUMNS) as well.

Before it was getting it's size data from curses, but curses is not
available to the readline based interface, so things would get out of sync.
The readline based interface had no way at all to know if there had been
any changes to the size of the window. 

I have changed it so that both the sides use the same callback function. The
event handler has been changed to call some clean up operations that
readlines needs and then puts in a request to call the resize function in 
the main event loop on the next pass. It does change a couple new parameters
that readline 6.3 introduces, rl_change_environment and rl_prefer_env_winsize
They make it so readline does not set ROWS or COLUMNS in the environment,
and seems to be suggested by the ncurses FAQ [1]. The previous method
that handedled resizing after getting input from curses, along with some
support code, has been removed.

The only problem I am aware of with this patch is that until the first
character is typed after resizing in curses mode, you do not see
the contents of the command window. This seems to have no impact on any
other function. Resizing with, without, or any number of switches in
between curses and readline modes were unable to produce a out of sync
size report for me. Without the patch, any resize operation shrinks the
size of the command portion of the window to 3 lines, which is retained
as the full height of the screen in readline mode until you exit the 
session.

I see no regressions in the test suite, even though this isn't the
sort of issue that automated testing is very good at.

CustaiCo

[1] http://invisible-island.net/ncurses/ncurses.faq.html#handle_resize

                === gdb Summary ===

# of expected passes            28624
# of unexpected failures        98
# of unexpected successes       1
# of expected failures          58
# of known failures             55
# of unresolved testcases       12
# of untested testcases         46
# of unsupported tests          184

---
 gdb/ChangeLog      | 14 ++++++++++++++
 gdb/tui/tui-data.c | 16 ----------------
 gdb/tui/tui-io.c   | 21 ---------------------
 gdb/tui/tui-win.c  | 40 +++++++++++++++++++++++++++++++++++-----
 gdb/utils.c        |  7 +++++--
 5 files changed, 54 insertions(+), 44 deletions(-)