FTP Extension SSL issues + refactor/cleanup of UI logic

[dd32]

As discussed last night on #wordpress-dev, There exists cases where people are getting invalid username/password when using the FTP Extension (Whilst the credentials are correct).

__lance__ tracked it down to SSL being selected, when the UI wasnt showing it as such.. It seems it was coming from $opt['ssl'], which AFAIK, Isnt actually set by WordPress at all (It could've been left over from an early revision..)

The attached patch cleans up some of the UI Logic as well, and takes into consideration FS_METHOD being set, which forces it in some cases.

Also, Includes an uncommited change, a class_exists() around the FS Abstraction file, To check if the class exists already before including a abstraction file, Its mainly for use when a plugin adds a 3rd-party FS Method file (Like my debug trace plugin does, No-wonder it never worked for anyone else)

[demetris]

I did not have any problems before, but I tried this just for regressions.

I tested on 4 different setups, of which 2 use FTP/FTPS for upgrades/updates.

Everything worked OK before, and everything works OK after.

[lance_]

Installed the patch, confirmed that this allows me to install plugins via ftp now. Thanks!

[westi]

(In [11495]) Fix plugin/theme upgrade issues when using ftp extension. Fixes #9980 props DD32.