This change disables the reporting of strict standard errors in PHP 5.4,
in PHP versions prior to 5.4 E_STRICT wasn't part of E_ALL so for
these versions this doesn't cause any change (however E_STRICT is
available in all versions of PHP 5 so this doesn't cause any problems).
See also FS#2427.

All calls to the Sitemapper were static function calls, this caused
notices because they weren't static, with this commit they are marked as
static. Furthermore two FIXME comments were removed as dbglog now checks
if debugging is enabled.

Template authors need to update their _mediamanager.css

This could happen if a sidebar is rendered before the page (populating
$TOC) and the page itself had no own TOC (no headers).

fixed link in popup media manager to fullscreen media manager to open in correct namespace (FS#2401)

For some reason trailing/leading underscores were allowed when uploading
files. But the rest of the code (eg. listing or downloading files) never
supported this. This patch removes this special case for uploading files
to streamline ID cleaning of pages and media files.

On certain environments, stream_select might produce temporary errors
when file descriptors are running scarce.