add x13as

[h-vetinari]

For use in statsmodels, e.g. here.

[github-actions]

Hi! This is the staged-recipes linter and your PR looks excellent! 🚀

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/x13as/meta.yaml) and found it was in an excellent condition.
I do have some suggestions for making it better though...

For recipes/x13as/meta.yaml:

• License is not an SPDX identifier (or a custom LicenseRef) nor an SPDX license expression.

Documentation on acceptable licenses can be found here.

[h-vetinari]

Getting compilation errors:

$BUILD_PREFIX/bin/x86_64-conda-linux-gnu-gfortran -O2  -c -o adpdrg.o adpdrg.f
adpdrg.f:409:72:

  409 |      &               'after end of LS sequence (LSS)',T)
      |                                                                        1
Error: More actual than formal arguments in procedure call at (1)

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/x13as/meta.yaml) and found it was in an excellent condition.