Device htc vision

Hi,

This is a merge request to add support for the HTC Desire Z, aka HTC G2, aka HTC Vision. It's based on the device-htc-vision branch that cmdrwgls created around a year ago. I've added the following changes:

• make pmbootstrap kconfig check pass
• enable CONFIG_MSM_KSGL
• enable compilation with GCC 8
• add deviceinfo_flash_offset_base to deviceinfo as apparently that is required for HTC devices (#145 (closed))

Unfortunately it still won't boot. When I try (pmbootstap flasher boot), the device simply gets stuck displaying a green htc logo on a white background. I've tried the maximum-attention initramfs hook, but without success, it doesn't even seem to get that far. One possible person to contact might be milaq since he is providing current LineageOS builds for this device and is apparently able to produce a working kernel image from that source tree. And if anybody has an idea about how to make this thing boot I'm all ears! Or if you can give some hint on how to troubleshoot this, I'd also be very interested. Note that I've also tried building this tree with GCC 6 and ended up with the exact same result.

//EDIT: I managed to get the device to boot, this should now be ready to merge.