Refactor all Silicon Laboratories targets to be CMake buildsystem targets. This removes
the need for checking MBED_TARGET_LABELS repeatedly and allows us to be
more flexible in the way we include MBED_TARGET source in the build.
A side effect of this is it will allow us to support custom targets
without breaking the build for 'standard' targets, as we use CMake's
standard mechanism for adding build rules to the build system, rather
than implementing our own layer of logic to exclude files not needed for
the target being built. Using this approach, if an MBED_TARGET is not
linked to using `target_link_libraries` its source files will not be
added to the build. This means custom target source can be added to the
user's application CMakeLists.txt without polluting the build system
when trying to compile for a standard MBED_TARGET.
* Updates driver library to v2.3.1 (2018q1) for bugfixes and convenience functions
* Provides library in correct format (2-byte wchar_t flag) for compiling with ARMCC (#6695 uncovered by #6577)
* Reverts to using a statically-allocated packet buffer since malloc is not thread-safe (and the asserts have been turned on)
Due to limitation in the mbed website backend (board names need to be <= 19 characters), we are shortening the CLI target names from THUNDERBOARD to TB.
@screamerbg
As asked by @0xc0170 in PR #3934, we won't be using device_has for indicating RF/Crypto features any longer. RF config options moved to the SL_RAIL lib.json, crypto config options will come with mbedTLS integration.
mbed compile doesn't support two different FEATURE_X folders being merged, so we'll have to move our nanostack driver into the Nanostack folder for the time being.