Removed `digitalWrite(GREEN_LED, HIGH);`

Removed `digitalWrite(GREEN_LED, HIGH);`
Major change to analogWrite() - It now gracefully determines whether a particular pin is already configured for PWM, and does a synchronized update of the CCRx register after a while() delay.
Update - Timer_B now modified to use its built-in double-buffering feature, Timer_A still uses a busy-wait.  Next update should remove the busy-wait in lieu of an interrupt-driven feature.
Initial commit; Timer_A interrupt-driven updates
Forgot 'volatile' for the CCR double-buffer variables since they're read in an ISR.  Tested with F5529 LP; seems to work!
Tried TA and TB pins.
Modified logic; PxSEL bits are only set AFTER the initial PWM value is written to the CCR register, to avoid glitching due to prior timer runs + prior CCR values being intact.
Merge branch 'issue_372' of https://github.com/energia/Energia into issue_372