Remove underscores from private/protected members names

[mateuszsip]

Closes #3004

[Majkl578]

Restarted the failing build. Although not a blocker, can you please look into the CS issues? We currently have a rule that modified code should follow Doctrine CS (even if rest of the code doesn't yet).
We should also consider a BC layer for master in separate PR.
Otherwise 👍.

[morozov]

@Majkl578 I believe we could ignore the code style issues for massive automated changes like this as long as they don't introduce new issues. Or maybe whitespace/alignment issues could be fixed here as well.

What kind of a BC layer do you have in mind? For protected methods, we could have the deprecated old methods which invoke the new ones. But what about properties?

[Ocramius]

Benefits here are too marginal to consider the patch, compared to massive BC concerns. Closing as won't fix.

[Majkl578]

How about reconsidering what really needs to be protected and for those provide final protected getter (and make fields private)?

[Ocramius]

@Majkl578 anything that we can make final probably should be, but we should do that before considering any style changes. That is a design change :-)

[morozov]

Besides the above, we still can fix private methods and properties and protected methods and properties in the non-abstract test classes.

As for private/protected as such, there's also lack of consistency across the codebase. For instance, MysqliConnection::_conn if private but OCI8Connection::dbh is protected.