Add support for remote CAN frames

Fixed bug where outgoing messages always had DIR bit set, even if
message type was CANRemote.
Fixed TODO where incoming messages were always assigned message type
CANData even if the message was remote
Changed filter setup to no longer set MDIR bit in receive filter; this
allows remote messages to pass through the filter.
Merge pull request #346 from devanlai/LPC11CXX-RTR

Add support for remote CAN frames on LPC11CXX