Add server side ncurses terminal

This adds a chat console the server owner can use for administration
or to talk with players.
It runs in its own thread, which makes the user interface immune to
the server's lag, behaving just like a client, except timeout.
As it uses the same console code as the f10 console, things like nick
completion or a scroll buffer basically come for free.
The terminal itself is written in a general way so that adding a
client version later on is just about implementing an interface.

Fatal errors are printed after the console exists and the ncurses
terminal buffer gets cleaned up with endwin(), so that the error still
remains visible.

The server owner can chose their username their entered text will
have in chat and where players can send PMs to.
Once the username is secured with a password to prevent anybody to
take over the server, the owner can execute admin tasks over the
console.

This change includes a contribution by @kahrl who has improved ncurses
library detection.

src/chat.h

@@ -25,7 +25,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include <vector>
 #include <list>
 
-// Chat console related classes, only used by the client
+// Chat console related classes
 
 struct ChatLine
 {
@@ -123,7 +123,7 @@ private:
 	u32 m_scrollback;
 	// Array of unformatted chat lines
 	std::vector<ChatLine> m_unformatted;
-	
+
 	// Number of character columns in console
 	u32 m_cols;
 	// Number of character rows in console
@@ -213,7 +213,7 @@ private:
 	std::wstring m_line;
 	// History buffer
 	std::vector<std::wstring> m_history;
-	// History index (0 <= m_history_index <= m_history.size()) 
+	// History index (0 <= m_history_index <= m_history.size())
 	u32 m_history_index;
 	// Maximum number of history entries
 	u32 m_history_limit;