build failure in TUI

[Tom Tromey <tromey@redhat.com>]

I just updated and rebuilt the gdb trunk on x86 Red Hat Linux 7.3.

I get this:

gcc -c -g -O2    -I. -I../../src/gdb -I../../src/gdb/config -DLOCALEDIR="\"/home/tromey/gnu/baseline-gdb/install/share/locale\"" -DHAVE_CONFIG_H -I../../src/gdb/../include/opcode -I../../src/gdb/../readline/.. -I../bfd -I../../src/gdb/../bfd  -I../../src/gdb/../include -I../intl -I../../src/gdb/../intl  -DMI_OUT=1 -DTUI=1 -I../../src/gdb/tui -DGDBTK -DUI_OUT=1 -Wimplicit -Wreturn-type -Wcomment -Wtrigraphs -Wformat -Wparentheses -Wpointer-arith -Wuninitialized -Werror ../../src/gdb/tui/tuiIO.c
cc1: warnings being treated as errors
../../src/gdb/tui/tuiIO.c: In function `tui_redisplay_readline':
../../src/gdb/tui/tuiIO.c:190: warning: comparison is always true due to limited range of data type
../../src/gdb/tui/tuiIO.c:193: warning: comparison is always true due to limited range of data type


This causes a failure because I configure with both --enable-tui and
--enable-gdb-build-warnings=,-Werror.

I looked at the code a bit.  I think the simplest fix may be to change
the definition of CTRL_CHAR (in readline/chardefs.h) to cast its
argument to `unsigned char' (and then remove the `>= 0' check).
However, I don't know the policy on changing readline, so I decided
not to send a patch.

Tom