* Move vector table to beginning of flash image. Modify a boot2 to use the table.
* Move binary info header up between ELF entry and reset handler
* Extract common routines from boot2_w25q080 into helper files
* Non-default boot2s: use common routines, make callable as void(*)(void)
* BSD3 headers on boot2 files (people might want to use them elsewhere)
* Promote binary info header to its own section, + comment/readability changes
* Fix scope of asminclude path (fixes user custom boot2 definitions)
* Rename symbol, clarify comment
