Bug#1062952: This package is not affected by time_t

[Dima Kogan]

Hi.

libmrcal-dev does not use time_t. I'm seeing the abi-compliance-checker
failure here:

  https://adrien.dcln.fr/misc/armhf-time_t/2024-02-01T09%3A53%3A00/logs/libmrcal-dev/base/log.txt

The cause is that the tool takes all the headers in /usr/include/mrcal
in an arbitrary order, and tries to #include them. That does not work
here. "mrcal-internal.h" should not be #included explicitly since it is
already #included by mrcal.h. Removing that header from the command in
the error log above makes the errors disappear.

Let me know what needs to happen to ingest that logic, to exclude mrcal
from this transition. This will make my life easier.

Thanks.