owncloud/apps — pull request #1614 by cweiske (2014-01-17 20:38:02+00:00)
Title: user_external: Check if extensions are enabled before using them

This patch checks if the relevant functionality is actually available
before using it for authentication:

1. check if function imap_open() exists before using it
2. check if smbclient executable exists during smb auth
3. check if ftp/ftps stream wrappers are registered before
using them for auth

This fixes a crash (white page) that happens when using IMAP authentication
and the IMAP extension is not installed.

This has been requested in PR #1579.