* Make memory sections configurable in linker files
* Dynamically determine vector location in flash for NVIC relocation
* Advertise bootloader support in targets.json
Moving the per-board clock configuration (which oscillators are available on the board, their frequencies, and which ones to use) as config options to the target database. This way, they're more easily overridable when third parties start creating boards with EFM32 MCUs
Now that we have targets.json, we get target inheritance and can use it to clean up the EFM32 folder structure.
* In the top-level EFM32 folder, there are now folders per MCU family (Giant, Leopard, ...)
* Those family folders contain the CMSIS headers in the 'device' subfolder, as well as global family headers (i.e. mapping of pins to peripherals)
* Inside of the family folder, there is a per-target folder containing target settings. In the future, we'll want to get rid of those by using the config system provided by targets.json