Initialize the I2S PLL in the system startup.
GPIO fixes to make digital input work.
Small fixes to make analog in work.
Changes to make port api work.
Remove empty files, and not ported driver code.
Make toolchain use hard float, and remove debugging statement.
Untested start to USB device support.
Refactoring of the mbed SDK:
- Provide a well defined HAL and API
- Keep separated the HAL implementations for the different targets
Unify mbed library sources
Remove stdio retargeting reference form cmsis: keep it as a standalone
object
Avoid object files clash for sources with the same name
Merge branch 'master' into STM32F4

Conflicts:
	workspace_tools/build_api.py
	workspace_tools/data/support.py
	workspace_tools/libraries.py
	workspace_tools/paths.py
	workspace_tools/toolchains.py
Use correct setting for -mfpu when building for Cortex-M4 targets, and
add a setting for using hard or soft floating point.
Merge branch 'cortex-m4-float-options' into STM32F4
Merge pull request #6 from spectaclelabs/cortex-m4-float-options

Use correct setting for -mfpu when building for Cortex-M4 targets, and add a setting for using hard or soft floating point.
KL05 - target ARM - gpio, us_ticker

  - cmsis - only one type of MCG at the moment
  - HAL - gpio pins
        - us_ticker
HAL removing code for API which is not ported yet
KL05 analog in+out, gpio irq

  - AnalogIn
  - AnalogOut
  - GPIO irq
  - target KL05 added
Serial API

  - serial UART0 added
  - correction in gpio irq (port b)
Refactor the build system:
* add sets of TARGET and TOOLCHAIN "labels"
Update README.md

Add community paragraph
KL05 Clocks, PWM, RTC, Serial

  - clock setup update
  - serial correction with core clock (define)
  - pwm defines
  - RTC clock