* Added platform/toolchain.h toolchain abstraction layer via macros:
OT_TOOL_PACKED_BEGIN
OT_TOOL_PACKED_END
OT_TOOL_DEPRECATED(symbol)
* Make pretty. Rekick travis-ci.
* Added doxygen. Resolved review comments.
* Fixed doxygen sample for OT_TOOL_PACKED to include type name.
* Renamed OT_TOOL_PACKED_FIELD to simplify code searches for usage. Fixed all nested instances to use new naming.
* Fixed OT_TOOL_PACKED_FIELD renaming in doxygen.
* Make pretty.
* Documentation clarifications.
* Moved example into overview section.
* Fixed sdcc comment.
* Revised sdcc comment.
* Fix code style in toolchain packed doxygen example.
* Fixed example. Moved toolchain test to better match code style.
* Added test for OT_TOOL_PACKED_FIELD.
* Added support for clang. Just routes to gcc __attributes__. Verified by running unit test through clang on macos.
Jonathan Hui