use pkg-config to look up ncurses deps to support things like split tinfo

--- a/configure.ac
+++ b/configure.ac
@@ -93,6 +93,7 @@
 AC_PROG_SED
 AC_PROG_YACC
 AM_PROG_LEX
+PKG_PROG_PKG_CONFIG
 
 AC_C_INLINE
 AC_C_CONST
@@ -304,9 +305,9 @@
 fi    
 
 if test "x$check_curses" != xno; then
-AC_CHECK_LIB(curses, tgetent, [],
-    [AC_CHECK_LIB(ncurses, tgetent, ,
-            [AC_MSG_ERROR(Required curses library not found.)])])
+    PKG_CHECK_MODULES([NCURSES], [ncurses])
+    CFLAGS="$CFLAGS $NCURSES_CFLAGS"
+    LIBS="$LIBS $NCURSES_LIBS"
 fi
 
 AC_CHECK_LIB(elf, elf_begin, [],