Makes app image booting more reliable (256-bit rather than 8-bit verification.)
Some measurements, time to boot a 655KB app.bin file and run to app_main() execution.
(All for rev 1 silicon, ie no 340ms spurious WDT delay.)
80MHz QIO mode:
before = 300ms
after = 140ms
40MHz DIO mode:
before = 712ms
after = 577ms
40MHz DIO mode, secure boot enabled
before = 1380ms
after = 934ms
(Secure boot involves two ECC signature verifications (partition table, app) that take approx 300ms each with 80MHz CPU.)
For config-only components, component.mk should now contain "COMPONENT_CONFIG_ONLY := 1"
Also refactored some of the generation of linker paths, library list. This required cleaning up the way the bootloader
project works, it's now mostly independent from the parent.
