Limited PWM period range

[LMESTM]

As first reported here under 'PwmOut generate wrong signal'
http://forums.mbed.com/t/pwmout-generate-wrong-signal/1418
it turns out that the PWM period is up to now limited to ~65ms for STM32 F3 family pwm control

[LMESTM]

Fix ongoing (under test)
Note: I tried to put myslef as the assignee but it seems I don't have rights to do so ...

[bcostm]

@0xc0170 I remember it was possible in the past to assign someone to an issue. Is it possible enable it again ?

[0xc0170]

We will need to create teams to be able to assign ppl outside of the mbed team. You can create a new issue for this, to be able to track the progress