Add the functions serial_tx_pinmap, serial_rx_pinmap, serial_cts_pinmap and serial_rts_pinmap to all targets.
Functions 'serial_break_set' & 'serial_break_clear' wrongly removed during 'SERIAL_FC disabled, critical section API Updation' commit. Due to this 'mbed compile' command for GCC_ARM tool fails to compile.
SERIAL_FC disabled, critical section API and Format changes updated