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.

1 files changed, 19 insertions, 1 deletions

diff --git a/src/util/string.h b/src/util/string.h
index 793baad0e..c8f60b802 100644
--- a/src/util/string.h
+++ b/src/util/string.h
@@ -32,8 +32,26 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #define STRINGIFY(x) #x
 #define TOSTRING(x) STRINGIFY(x)
 
+// Checks whether a value is an ASCII printable character
+#define IS_ASCII_PRINTABLE_CHAR(x)   \
+	(((unsigned int)(x) >= 0x20) &&  \
+	( (unsigned int)(x) <= 0x7e))
+
 // Checks whether a byte is an inner byte for an utf-8 multibyte sequence
-#define IS_UTF8_MULTB_INNER(x) (((unsigned char)x >= 0x80) && ((unsigned char)x < 0xc0))
+#define IS_UTF8_MULTB_INNER(x)       \
+	(((unsigned char)(x) >= 0x80) && \
+	( (unsigned char)(x) <= 0xbf))
+
+// Checks whether a byte is a start byte for an utf-8 multibyte sequence
+#define IS_UTF8_MULTB_START(x)       \
+	(((unsigned char)(x) >= 0xc2) && \
+	( (unsigned char)(x) <= 0xf4))
+
+// Given a start byte x for an utf-8 multibyte sequence
+// it gives the length of the whole sequence in bytes.
+#define UTF8_MULTB_START_LEN(x)            \
+	(((unsigned char)(x) < 0xe0) ? 2 :     \
+	(((unsigned char)(x) < 0xf0) ? 3 : 4))
 
 typedef std::map<std::string, std::string> StringMap;