Add Energy Micro EFM32 Giant Gecko IRQ list.
Add simple util to convert IRQ list into startup C file.
Add Energy Micro EFM32 Tiny Gecko IRQ list.
Add Energy Micro EFM32 Gecko IRQ list.
Add Energy Micro EFM32 Leopard Gecko IRQ list.
Add Energy Micro EFM32 Wonder Gecko IRQ list.
Support IRQ list with explicit IRQ numbers.

Useful for MCUs with gaps in IRQ vectors. Don't switch all IRQ list to new
format, because it's usually easier to diff lists without explicit numbers.
(It seems there're 2 vendor approaches here: 1) don't use gaps, just renumber
supported vectors (EFM32), 2) use same numbering for IRQs, just use gaps if
specific model doesn't support some IRQs (probably most other vendors)).
Add STM32F100 IRQ list.