lang/nim: Update to 1.4.0

• Update to 1.4.0
• Add a workaround to build doc in poudriere
• Remove patch-compiler_docgen.nim (fixed upstream)
• Add patch-koch.nim to disable Fusion build

Release notes:

• https://nim-lang.org/blog/2020/10/16/version-140-released.html

PR: 250458
Submitted by: Neal Nelson (maintainer)