Make iso8601_to_datetime a bit more compliant

[chrisscott]

With a valid ISO 8601 date string with dashes in the date or decimal fractions for seconds, this function will fail to parse it correctly. The attached patch updates the regex to optionally accept dashes and decimal fractions for seconds (which are ignored). It also uses a variable for the regex since it was duplicated.

[dd32]

This function doesn't handle 90% of the iso8601 formats it seems, for example, it chokes on something as basic as '2013-08-09T00:31:38Z' (even with the patch).

This needs serious unit tests and a patch that handles it as such.

[rmccue]

Whoa, the hell is this function? ​Here's my take from the REST API, which handles RFC3339 (a subset of ISO8601 that doesn't include all the unnecessary bits) which is usually used on the 'net. I'd be happy to build off that, but this giant regex seems unnecessary.

[ericmann]

Add some tests listing iso8601 dates and what they should be parsed to.

[ericmann]

Added a test function that lists several valid iso8601 dates and the mysql date they should be parsed to. Any patches submitted to this ticket will need to address these formats and pass the test (current implementation and existing patch don't quite meet that criteria).

[nacin]

Certainly would be nice to fix this. Thanks for the tests, ericmann.