Use widechars to display strings in the UI

This fixes a bug where printing a bunch of UTF8 chars with glyphs
that have a size > 1 would make the entire chat window disappear.
It also fixes an issue where said UTF8 chars would be truncated
and generally not display correctly.

src/toxic.h

@@ -23,6 +23,10 @@
 #ifndef TOXIC_H
 #define TOXIC_H
 
+#ifndef NCURSES_WIDECHAR
+#define NCURSES_WIDECHAR 1
+#endif
+
 #ifndef TOXICVER
 #define TOXICVER "NOVERS"    /* Use the -D flag to set this */
 #endif