replace textfilter functions with one-fits-all version

* replaces filtertext() with a version with a dozen of single filters
  that can be used in any combination
* defines classes of allowed characters for strings for various uses
  (see protocol.h line 153ff)
* now the allowed charset of, for example, player names is defined
  in one location only
* fixes issue #58

source/src/console.cpp

@@ -97,7 +97,7 @@ void renderconsole() { con.render(); }
 void clientlogf(const char *s, ...)
 {
     defvformatstring(sp, s, s);
-    filtertext(sp, sp, 2);
+    filtertext(sp, sp, FTXT__LOG);
     extern struct servercommandline scl;
     const char *ts = scl.logtimestamp ? timestring(true, "%b %d %H:%M:%S ") : "";
     char *p, *l = sp;
@@ -345,7 +345,7 @@ void mapmsg(char *s)
 {
     string text;
     filterrichtext(text, s);
-    filterservdesc(text, text);
+    filtertext(text, text, FTXT__MAPMSG);
     copystring(hdr.maptitle, text, 128);
     if(editmode) unsavededits++;
 }