[NUCLEO_F103RB] Remove PD_0/PD_1 pins

These pins are not present in the 64 pins package.
Merge branch 'master' of https://github.com/mbedmicro/mbed
I2C NAK fix
Merge remote-tracking branch 'upstream/master'
Merge pull request #286 from bcostm/master

[NUCLEO_F103RB] Remove PD_0/PD_1 pins
Merge pull request #287 from tkuyucu/master

Update with I2C fix