Recent changes to the way registers are handled broke reporting of AVX
registers (i.e. YMMx). This change restores the functionality by:
- concatenating the higher half of the YMMx registers to their
corresponding XMMx lower half (YMMx registers do not have an
independent DWARF register number)
- modifying the formatSSEReg function to handle them when they are
present.
Fixes#2033
Registers XMM1 and XMM2 get sometimes clobbered between the time we set
them and the panic. There is no guarantee that they won't in the go
spec so we shouldn't expect any register to keep its value. However
since this seems to only affect 1 and 2 let's try to use 9 and 10
instead.
