Potential fix for #646
[LPC824] Fix serial interrupt issues

Basically, this is same fix as
https://github.com/mbedmicro/mbed/pull/633
* Fix issue by handling interrupt type (TxIrq and RxIrq)
* ISR now correctly refers INTSTAT instead of STAT to get interrupt
cause
* Disable interrupt when updating vector table
* Tested by issue #616 test cases and serial_interrupt test
Merge pull request #655 from toyowata/master

Targets: LPC824 - Fix serial interrupt issues
Merge pull request #654 from bcostm/master

Exporters: STM32L053R8 - IAR exporter
Merge pull request #649 from rgrover/master

API: ticker casting fix (issue #649)
Merge branch 'master' of https://github.com/mbedmicro/mbed