lib/files.php: make use of === instead of ==
refactored/cleaned up lib/files.php
cleaned up get() logic
fixed get() to only send headers if requested (xsendfile could get in the way)
do no longer readfile() when already using mod_xsendfile or similar
switched zip file creation to ZipStreamer to create zip files directly in memory
Merge branch 'zipstreamer' of https://github.com/McNetic/owncloud_core into McNetic-zipstreamer

Conflicts:
	lib/private/files.php
updating 3rdparty
Merge branch 'master' into McNetic-zipstreamer
Merge branch 'master' into McNetic-zipstreamer

Conflicts:
	3rdparty
Merge pull request #7328 from owncloud/McNetic-zipstreamer

McNetic zipstreamer