Backport upstream fix for CVE-2026-59858 from commit
6b611b0d15603c52ebdad17172b0232b4f65704e. A crafted tags
file could execute arbitrary Ex commands when completing
struct/union members via C omni-completion. The fix escapes
the typename field before interpolating it into the :vimgrep
pattern in StructMembers(), preventing command injection.
A new test file validates both the security fix and that
normal struct-member completion continues to work.
CVE: CVE-2026-59858
Upstream patches:
- 6b611b0d15.patch
- d9ec676911
Resolves: RHEL-203886
