Change debugger to write packet via log's Writer (#1)

[almozavr]

Issue

Debugger prints debug-level messages via std log but prints packets via os.Stdout, so it makes impossible to use the Output from the global log, e.g. zap provides single point of configuration even for the global log, so still could be used for libraries logging setup.

Solution

Pass log#Writer() to the ber packet writer func.

Partly resolves #164

[stefanmcshane]

Please apply these changes to debug.go as well as v3/debug.go in order to merge.
Ill review this weekend to get them merged then!

Thanks,
Stefan

[johnweldon]

LGTM; please update with master and we'll merge it in.

[almozavr]

@johnweldon updated 👍 also, I've prettified commits a bit

[johnweldon]

LGTM; thank you!

[lozbrown]

@johnweldon @almozavr

This change seems to have broken an automated install for me, the go get command now gives the following error.

"go/src/github.com/go-ldap/ldap/debug.go:28:19: undefined: log.Writer"

[johnweldon]

This change seems to have broken an automated install for me, the go get command now gives the following error.

"go/src/github.com/go-ldap/ldap/debug.go:28:19: undefined: log.Writer"

can you specify exactly what your go get invocation is, as well as the version of Go you're using?