Push sanity check to 15 Meg maximum. (#928)

Maximum useable space for contact data is 15 Megs. Above that, we are into the OEM zone and bad things are likely happening elsewhere anyway.

applet/src/usersdb.c

@@ -123,7 +123,7 @@ static int find_dmr_user(char *outstr, int dmr_search, const char *data, int out
 
     // filesize @ 20160420 is 2279629 bytes
     //          @ 20170213 is 2604591 bytes
-    if (datasize == 0 || datasize > 9437183)  // 9 Meg sanity limit
+    if (datasize == 0 || datasize >15728639)  // 15 Meg sanity limit
        return(0);
 
     const char *data_start = next_line_ptr(data);