Complete support for GPIO interrupts.
Revert "Complete support for GPIO interrupts."

This reverts commit df067bd4e9d6981c04c11e2b7c6a3e1495cc4b8e.
Merge branch 'master' of https://github.com/matthewelse/mbed

ommit df067bd4e9d6981c04c11e2b7c6a3e1495cc4b8e.