Revert "bc: Vendor import of Gavin Howard's bc version 3.2.6"
This reverts commit 601ac82194693fcae9d7d2a7ec7d66ebaf3fd61e.
Seems that git cherry-pick mis-merges files for this software.
It associates files in completely unrelated sub-trees with same name
files from this package, e.g. README.md and .gitignore.
My attempt to fix the mis-merge was incomplete and wrong.
Therefore I'm reverting the commit that as a result of my failed
attempt at conflict resolution lead to README.md and .gitignore
in the top source directory to be deleted.
This mistake has been carried over to releng/13.0, which now
also lacks README.md and .gitignore in /usr/src.
I'll try to re-apply the failed commit over the next hours and to get
the fix merged to releng/13.0 with re approval.