[stm32f4] add I2C frequencies

STM32F4 allows I2C frequencies up to 42 MHz, this commit adds the missing
defines.
[build] Remove PyYAML dependency

This converts all the YAML files to JSON files, as json parsing is built
into python instead of being a separate library requiring installation.

YAML is a superset of JSON, but putting comments in is not quite as obvious
as it is in yaml.

The following glue was used to convert yaml to json:
python -c 'import sys, yaml, json; json.dump(yaml.load(sys.stdin), sys.stdout, indent=4)' < $1 > $2

Clearly I haven't tested this on every single platform, and this
doesn't address the large blobs of yaml in the lpc4300 scripts directory,
only the cortex NVIC generation process.

I've tested a few IRQ driven example apps, and I've checked the generated
output of some known cases like the LM3s that has explicit gaps, and they are
all generated correctly.
[CM3] Add core interrupt masking for easy creation of atomic blocks
[CM3] Add support for Cortex M interrupt masks

FIX: add doxygen documentation to the module
[CM3] Add atomic operation support

Tested with -O0, -O2 and -Os generating correct code with gcc-arm-embedded 2013q2.
note -std=c99 or newer needed
[Stylecheck] Correct style in the CM3 addition
[CM3] Add register definitions for Debug Watch Trace point.

Add provision functions for the use of CPU counter as a high-resolution timer for code benchmarking purposes
[CM3:DWT] Add the file to library build process for each target
* unnecessary PG bit clearing removed from flash word and half-word programming to improve speed
* missing PG bit set is inserted at word programming
Add the linker generator makefile

Example of use is included in the file header
Add example to the device database file
Add Readme to linker script generator dir
Add Example makefile to linker script generator dir
[GENLINK] correct the whitespace bug
[GENLINK] Add Test suite + simple test
[GENLINK] Add test patterns
[GENLINK] Code Cleanup
[GENLINK] Edit the documentation to match current version
[GENLINK] Moved linker template source to ld directory
[GENLINK] Make tests in paralell

usage:

make genlinktests -j

speedup: 4 times on 8-core system