gdb: add --with-curses to --configuration output

gdb: add --with-curses to --configuration output

'gdb --configuration' does not mention if GDB was built with curses.
Since b5075fb68d4 (Rename to allow_tui_tests, 2023-01-08) it does show
--enable-tui (or --disable-tui), but one might want to know if GDB was
built with curses independently of the availability of the TUI.

Since configure.ac uses AC_SEARCH_LIBS to check for the curses library,
we do not get an automatically defined HAVE_LIBCURSES symbol in
config.in. We do have symbols defined by AC_CHECK_HEADERS
(HAVE_CURSES_H, etc.) but it would be cumbersome to use those in
print_gdb_configuration because we would have to check for all 6 symbols
corresponding the 6 headers listed. This would also increase the
maintenance burden if support for other variations of curses are added.

Instead, define 'HAVE_LIBCURSES' ourselves by adding an
'action-if-found' argument to AC_SEARCH_LIBS, and use it in
print_gdb_configuration.

While at it, remove the condition on 'ac_cv_search_waddstr' and set
'curses_found' directly in 'action-if-found'.

Change-Id: Id90e3d73990e169cee51bcc3e1d52072cfacd5b8
Approved-By: Simon Marchi <simon.marchi@efficios.com>