Gauge filenames

[rjleveque]

This addresses #541, creating filenames in the same format as previously if the gauge number has 5 or fewer digits, e.g. gauge00012.txt, but allows up to 15 digits, e.g. gauge123456789.txt.

If this seems ok, I'll do the same thing in amrclaw.

Note that gauges are still read in fine for plotting regardless of the number of digits, with no changes needed in pyclaw.gauges.GaugeSolution.

Note that this is implemented via these two lines (where numstr is a character variable):

write (numstr,'(I0.5)') num
gauges(i)%file_name = 'gauge'//trim(numstr)//'.txt'

This is a much cleaner way to do it than the old way of starting with gaugexxxxx.txt and changing one character at a time!

We should eventually make this change also in creating filenames like fort.t0001, in valout.f90, both for cleaner code and greater flexibility if the user needs more digits than we originally planned for.

[mandli]

Works for the examples I tested.

[rjleveque]

Thanks @mandli.

In further testing I realized that the maximum gauge number is still limited by the fact that this is read in and stored as a 4-byte integer, so not larger than 2147483647. But at least it now allows any 9-digit or shorter gaugeno.

[mandli]

I noticed that but I figured we can work out the warning/error message when added to AMRClaw where the Python data stuff is handled.

[rjleveque]

Good idea, I'll modify the amrclaw PR I just did...