compiler: support new numeric literal syntax

Support 0b, 0o, and hex floats.

Tested against test/literal2.go in the gc repo.

Updates golang/go#12711
Updates golang/go#19308
Updates golang/go#28493
Updates golang/go#29008

Change-Id: I2ab01255f529880a2bd8603107e3e1ae03a7a3e5
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/189718
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
2 files changed