Change the i386 code to pass the interrupt vector as a separate argument
rather than embedding it in the intrframe as if_vec. This reduces diffs
with amd64 somewhat.

• Remove cf_vec from clockframe (it wasn't used anyway) and stop pushing dummy vector arguments for ipi_bitmap_handler() and lapic_handle_timer() since clockframe == trapframe now.
• Fix ddb to handle stack traces across interrupt entry points that just have a trapframe on their stack and not a trapframe + vector.
• Change intr_execute_handlers() to take a trapframe rather than an intrframe pointer.
• Change lapic_handle_intr() and atpic_handle_intr() to take a vector and trapframe rather than an intrframe.
• GC struct intrframe now that nothing uses it anymore.
• GC CLOCK_TO_TRAPFRAME() and INTR_TO_TRAPFRAME().

Reviewed by: bde
Requested by: peter