support interrupts

[WebFreak001]

currently interrupts must be done by defining methods using magic names like __vector_4 for interrupt 4 (which needs to be looked up from the specific board header)

In C there is a macro

ISR(INT0_vect)
{
    // code
}

which can achieve this easily.

In D I would like to still provide auto completion support (= not all code as string), while also avoiding wrong usage like trying to call the interrupt as a function (because it returns using reti instead of ret)

A possibility would be a template mixin with a delegate parameter or a function name that gets called. Would still need some work to make it work with betterC (even with CTFE) right now though.

(needs input)

[ErnyTech]

LDC is currently unable to use calling convection for interrupts, we need to set Calling CallingConv::AVR_INTR for non-blocking interrupts and CallingConv::AVR_SIGNAL for blocking interrupts (See https://llvm.org/doxygen/CallingConv_8h_source.html).

I am working on several patches for LDC including this one to improve support