google-api-go-generator: add helpers for converting basic types to pointers.
google-api-go-generator: add helpers for converting basic types to pointers.

These helpers are derived from github.com/golang/protobuf/proto.
Float32 has been dropped, as float32 does not appear in the googleapi
generated code.

Change-Id: Ifc36c15c1b254370dbeaf243f9fbcfc93440b0a3
Reviewed-on: https://code-review.googlesource.com/3363
Reviewed-by: Michael McGreevy <e70fec140fa6773c6cfd45cb9b436bd6334f4c24@golang.org>

google/google-api-go-client,likaiwalkman/google-api-go-client,digideskio/google-api-go-client,googleapis/google-api-go-client,webhost/google-api-go-client,80nashi/google-api-go-client,stephenwithav/google-api-go-client,googleapis/google-api-go-client,google/google-api-go-client