Fix atanisoft#17

The function commands were not being interpreted correctly as part of
the DCC++ text based protocol stream. The wrong set of functions were
being enabled due to missing guards on the bit masking.

src/LocomotiveManager.cpp

@@ -55,7 +55,7 @@ void LocomotiveManager::processFunction(const std::vector<String> arguments) {
   // check this is a request for functions F13-F28
   if(arguments.size() > 2) {
     int secondaryFunctionByte = arguments[2].toInt();
-    if(functionByte & 0xDE) {
+    if((functionByte & 0xDE) == 0xDE) {
       for(uint8_t funcID = 13; funcID <= 20; funcID++) {
         loco->setFunction(funcID, bitRead(secondaryFunctionByte, funcID-13));
       }
@@ -68,11 +68,11 @@ void LocomotiveManager::processFunction(const std::vector<String> arguments) {
     // this is a request for functions FL,F1-F12
     // for safety this guarantees that first nibble of function byte will always
     // be of binary form 10XX which should always be the case for FL,F1-F12
-    if(functionByte & 0xA0) {
+    if((functionByte & 0xA0) == 0xA0) {
       for(uint8_t funcID = 9; funcID <= 12; funcID++) {
         loco->setFunction(funcID, bitRead(functionByte, funcID-9));
       }
-    } else if(functionByte & 0xB0) {
+    } else if((functionByte & 0xB0) == 0xB0) {
       for(uint8_t funcID = 5; funcID <= 8; funcID++) {
         loco->setFunction(funcID, bitRead(functionByte, funcID-5));
       }