MDL-35469 fix Gecko based browser checks

The problem is that latest firefox versions stopped using dates because they lost the meaning over the time.
MDL-25948 upgrade: Fixing issues with upgrade from < 1.7 to 2.x.
Merge branch 'w42_MDL-35469_m21_geckover' of git://github.com/skodak/moodle into MOODLE_21_STABLE
MDL-36346 - YUI2 SWF vulnerability
Merge branch 'MDL-36346_21' of git://github.com/pauln/moodle into MOODLE_21_STABLE
Backport MDL-29872 to 21_STABLE
Automatically generated installer lang files
MDL-36346 - YUI2 SWF vulnerability, part 2
Merge branch 'MDL-36346_21' of git://github.com/pauln/moodle into MOODLE_21_STABLE
MDL-35558 mod_data: Show only own entries while there are required pending.
MDL-33791 Portfolio: Fixed security issue with passing file paths.
Merge branch 'install_21_STABLE' of git://git.moodle.cz/moodle-install into MOODLE_21_STABLE
weekly release 2.1.8+
MDL-25948 upgrade: Check that field does not match defaults before editing.
Merge branch 'MDL-25948_m21' of git://github.com/markn86/moodle into MOODLE_21_STABLE
MDL-25948 upgrade: Avoid overlaping with weeklies
Moodle release 2.1.9
Automatically generated installer lang files
weekly release 2.1.9+
MDL-36668 - mod/data: Removed duplicate data_content join in simple searches.

Thanks to Patrick Pollet (patrick.pollet@insa-lyon.fr) for his patch