Update profiling.rst

There is some confusion about how to enable profiling for queries. This will save some time for devs who want to debug their generated SQL.
Update profiling.rst

correcting rst syntax
Added _display documentation.
[ci skip] Update changelog
[ci skip] Update changelog
Remove CI_Encrypt::_xor_encode()
Add support for non-ASCII domain names in FV & Email classes' valid_email()

Depends on the Intl extension
Fixed code style.
reduced line length.
Merge pull request #3074 from aanbar/output_documentation

Added _display documentation.
Updating table template prototype id documentation

Updating template prototype in documentation to reflect the actual
template prototype in the table library.
Add a changelog entry in Pagination Library section
Fixed a changelog entry
Fixed the changelog entry again
Merge branch 'develop' of /Users/neko/github/CodeIgniter/user_guide_src/ into develop_japanese