Make interpolator file path buffer bigger

[menzel-gfdl]

Description
Makes an interpolator buffer bigger so that file paths that are > 64 and <=128 characters will work.

Fixes #1467

How Has This Been Tested?
I have been using this buffer size in another branch and it hasn't caused any issues.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included
• make distcheck passes

[thomas-robinson]

@menzel-gfdl can you check the boxes please on this PR.

[menzel-gfdl]

@thomas-robinson Done!