This fixes the prior logic that relies on the (*)curses library
and header existing in compiler-derived default locations
such as /usr/include, and /usr/lib. However, if the package manager
happens to not install them there, then they will not be found
and the check will fail.
Four scenarios:
1. `./configure` or `./configure --enable-debug=no` produce:
(no mention of debugger; configure continues)
2. `./configure --enable-debug=wrong` produces:
configure: error: --enable-debug=wrong was requested but the value "wrong" is invalid
(terminates with exit code 1)
3. `./configure --enable-debug` produces:
config.h:
defines C_DEBUG 1
With only ncurses library installed:
configure: debugger was requested, finding curses library ...
checking for NCURSES... yes
configure: debugger enabled using the ncurses library
Makefile:
CPPFLAGS = ... -D_DEFAULT_SOURCE -D_XOPEN_SOURCE=600 -I/usr/local/ncurses ...
LIBS = ... -L/usr/local/ncurses -lncurses -ltinfo ...
With only ncursesw installed:
configure: debugger was requested, finding curses library ...
checking for NCURSES... no
checking for NCURSESW... yes
configure: debugger enabled using the ncursesw library
Makefile:
CPPFLAGS = ... -I/opt/ncursesw ...
LIBS = ... -L/opt/ncursesw -lncursesw ...
With only pdcurses isntalled:
configure: debugger was requested, finding curses library ...
checking for NCURSES... no
checking for NCURSESW... no
checking for PDCURSES... yes
configure: debugger enabled using the pdcurses library
Makefile:
CPPFLAGS = ... -I/usr/local/pdcurses ...
LIBS = ... -L/usr/local/pdcurses -lpdcurses -ltinfo ...
Without any curses library installed:
configure: debugger was requested, finding curses library ...
checking for NCURSES... no
checking for NCURSESW... no
checking for PDCURSES... no
configure: error: Package requirements were not met:
<pkg-info prints info about missing package>
(terminates with exit code 1)
4. `./configure --enable-debug=heavy` produces same as above, but:
config.h:
defines C_DEBUG 1
defines C_HEAVY_DEBUG 1
The configure message mentions heavy, for example:
configure: debugger was requested, finding curses library ...
checking for NCURSES... yes
configure: debugger with heavy debugging enabled using the ncurses library
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