Fix command-line processing of p/P option.

Update docs to describe the p/P options.

Fixes #4 (better late than never..)

README.md

@@ -92,6 +92,7 @@ The available settings are:
  * i/I: FEC enabled / FEC disabled
  * j/J: Mode A/C disabled / Mode A/C enabled
  * k/K: no special filtering / do not send DF0/4/5 (only in Beast-Classic mode)
+ * p/P: disable/enable position-message reporting (only in Radarcape mode)
 
 The h/H setting is understood but ignored; hardware flow control is always
 used.

splitter_main.cc

@@ -111,7 +111,7 @@ namespace beast {
         po::validators::check_first_occurrence(v);
         const std::string &s = po::validators::get_single_string(values);
 
-        static const boost::regex r("[cdefghijbrvCDEFGHIJBRV]*");
+        static const boost::regex r("[cdefghijbrvpCDEFGHIJBRVP]*");
         if (boost::regex_match(s, r)) {
             v = boost::any(beast::Settings(s));
         } else {