README-developer: add contrib instructions, and update

[efiring]

No description provided.

[efiring]

@DocOtak is there anything else that you think should be added?

[DocOtak]

@efiring That is probably good enough to avoid the easy style mistakes. There is a mix of tab and space characters which look ok in vim but really mess things up in the github diff (and probably other text editors).

Do we want to have an alphabetical ordering for added functions? I think they are currently this way because that is how cat stuck the individual files together.

It's probably my inexperience with C, but I had a difficult time figuring out what all the test_sub1 type functions were for in gsw_check_functions.c, eventually I figured out it was for functions that had pointers passed into them for return values (to support multiple return values)

[efiring]

@DocOtak The present set of files should be nearly tab-free--I might have left a few tabs in the files generated by scripts.
gsw_check_functions.c is probably hard to understand for anyone, regardless of experience level; if you would like to add some explanatory comments there, and/or some notes about it in the README-developer, that would be most welcome.
Ordering: yes, the alphabetical ordering is an artifact, but it's probably as good as anything, so we might as well keep it. I have added a paragraph to that effect.

[DocOtak]

@efiring oh, I meant there was a mix of tabs and spaces in this README-developer file, sorry for not being specific.

[efiring]

Ouch! I thought my editor was fixing that, but evidently it is configured to do so only for recognized source files. I will fix it.

[PaulMBarker]

Hi,

I can not work out how to start a new topic, so I am going from here.

We have a computer programmer who is going to spend some time translating the matlab code to C.
I am guessing they will not get all of the missing codes converted but they will make a contribution. I have been asked to make a list of which programmes they want done in order of importance. Do you have a preference for which programmes are prioritised ?

Paul.