chg: Separate header to include ncurses headers

This concentrates differences between different platforms in a more central place.

src/lib/ncurses/ncurses.hpp

+#pragma once
+
+#ifdef __FreeBSD__
+#include <ncurses/cursesw.h>
+#else
+#include <ncursesw/ncurses.h>
+#endif

src/ui/view.cpp

-#ifdef __UNIX__
-	#include <ncurses/cursesw.h>
-#else
-	#include <ncursesw/ncurses.h>
-#endif
+#include "lib/ncurses/ncurses.hpp"
 
 #include "ui/view.hpp"