Rely on pkg-config to find the proper ncurses.h

On Ubuntu, /usr/include/ncursesw/ncurses.h is a symlink to ../ncurses.h.
On Gentoo, however, /usr/include/ncurses.h and
/usr/include/ncursesw/ncurses.h are different files, and only the latter
defines the wide character functions: we need to give the compiler the
proper -I flag.

For the sake of portability, ask pgk-config for the correct compiler
flags (including -I). Default to the flags used on Gentoo, which also
work on Ubuntu.

Makefile

@@ -2,6 +2,7 @@ DESTDIR   ?=
 PREFIX    ?= /usr/local
 MANPREFIX ?= $(PREFIX)/man
 CFLAGS += -Wall -Wextra
+CFLAGS += `pkg-config --cflags ncursesw 2>/dev/null || echo '-D_DEFAULT_SOURCE -D_XOPEN_SOURCE=600 -I/usr/include/ncursesw'`
 LDLIBS += `pkg-config --libs ncursesw 2>/dev/null || echo '-lcursesw -ltinfo'`
 torture: LDLIBS = -lm
 

ttyplot.c

@@ -5,7 +5,6 @@
 // Apache License 2.0
 //
 
-#define _XOPEN_SOURCE 500  // Get ncurses wchar_t support from SUSv2 (UNIX 98)
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>