Version 3 notes

Install:

    $ go get modernc.org/crt/v3

Version 3 is the transition from "all scalars are signed integers" (the QBE
model) to the more traditional "integers have signedness and pointers are not
exactly the same as integers" that is used by modernc.org/ccgo/v3. However, all
C pointers are of the same Go type: uintptr.
