added module_dir for just module code, otherwise should be the same as previous
Add 'hl7_module_dir/' from commit 'b90f085090d33c19f618e17963d6812a9c0c9f18'

git-subtree-dir: hl7_module_dir
git-subtree-mainline: b90f085090d33c19f618e17963d6812a9c0c9f18
git-subtree-split: b90f085090d33c19f618e17963d6812a9c0c9f18