Allow for escaped COM ports like \\.\COM3

https://github.com/Hamlib/Hamlib/issues/337

src/misc.c

@@ -1392,6 +1392,9 @@ int HAMLIB_API parse_hoststr(char *hoststr, char host[256], char port[6])
 
     if (strncasecmp(hoststr, "com", 3) == 0) { return -1; }
 
+    // escaped COM port like \\.\COM3
+    if (strstr(hoststr,"\\")) { return -1; }
+
     // bracketed IPV6 with optional port
     int n = sscanf(hoststr, "[%255[^]]]:%5s", host, port);