Handling of UTC datetime without padding 0 & degree at 360

[LarryZhou]

Hi, @airbreather,

I worked in the same team as Loren Halvorson who made the last commit of this package. Our recent work on Gpx uncovered a few data forma issues. Would you mind considering the following 3 minor changes? I will create a PR.

• UTC datetime value without padding 0, like "2024-03-23T18:6:8Z". It fails the current parsing. But when "T" is replaced with a space, the value can be successfully parsed.
• The range for degree (magvar) is [0, 360). But we have a data source that sometimes provides a max value of 360. Since we can't change the source, will it be OK to accept 360 as a valid value but reset it to 0.
• Similarly for longitude, the spec range is [-180, 180). It will be very helpful if 180 can be accepted as valid value and but reset it to -180.