spiflash: Add spiflash_is_idle

So we can tell when it's safe to enter STOP mode.
llwu: Initial commit of register definitions
rtc: Add alarm support
Merge pull request #89 from bgamari/rtc

rtc: Add alarm support
smc: Initial commit of register definitions
Merge pull request #88 from bgamari/llwu

Add register definitions for LLWU and SMC

As well as a quite unrelated spiflash utility.
FTM: Use enum value instead of literal
Merge pull request #91 from bgamari/fixes

FTM: Use enum value instead of literal
toolchain: add more K20 series targets

To allow them all to use the same startup code and such I replaced the
hardcoded ifeq in toolchain/lib/mchck/Makefile.part with a check on a
new variable called TARGET_FAMILY. It's set to 'K20' in all the target
.mk files to show they're all using the K20 code.
toolchain/pack-sections: fix knapsack

Two bugs:

- do not overwrite argument `w' with loop variable
- check whether section fits to avoid negative array indices

Discovered-by: Derek Mulcahy