Improve handling of CDC ACM line state

- For the CC2538, simplify handling of USB_CDC_ACM_LINE_STATE
  events. Ignore the Carrier Control (RTS) bit when receiving
  a SET_CONTROL_LINE _STATE request, we are a full duplex device.
- Improve behaviour of the CC2531 USB stick when there is no
  process on the host to read IN data. Basically, we adopt the
  CC2538 approach and we only send data when a DTE is present
Merge pull request #199 from g-oikonomou/cc253x-cdc-acm-line-state-fix

Improve handling of CDC ACM line state
CC2538 Documentation typo and grammar fixes
Change the InfoPage Location of the IEEE address
Merge pull request #202 from g-oikonomou/cc2538-minor-fixes

CC2538 IEEE address location and documentation fixes
tapdev: Fix using an uninitialized buffer
Add missing include

Fix log_message() undefined warning.
win32: Fix cygwin build

size_t is declared in sys/types.h
Merge pull request #203 from mmuman/cleanup-and-fixes-002

Cleanup and fixes 002