gerrit: add ability to pass QueryChangesOpt to GetChangeDetail
gerrit: add ability to pass QueryChangesOpt to GetChangeDetail

The existing implementation of GetChangeDetail does not allow for
an optional QueryChangesOpt. QueryChangesOpt adds the ability to
pass options such as CURRENT_FILES and CURRENT_REVISION in order
to receive a more detailed ChangeInfo struct.

Change-Id: I7925e75821538b2720fff7d62c8404ed97e18791
Reviewed-on: https://go-review.googlesource.com/34922
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/build,golang/build,golang/build,golang/build