PHP 5.4 strict warnings prevented

As committed on master branch:
- https://github.com/woothemes/woocommerce/commit/7c7e0ec9f4575ab91661326eb238a9b7c1e8cc97#comments
Merge pull request #3613 from thenbrent/release-2-0-14

Small WP 3.6 patches @coenjacobs can you move to 2.1 as well
Lock files - prevent full path disclosure. Fixes #3580.

@coenjacobs .14
Croatia is EU Fixes #3615.

@coenjacobs .14
Fix result count display when posts_per_page is set to -1

When your posts_per_page is set to -1 the display is output as `Showing 1–-1 of 15 results` when displaying all items when it would be better to show `Showing all 15 results`
Update post_date_gmt when changing order date