Merge pull request #496 from adierking/tailq

shims: fix TAILQ_CONCAT() edge cases
Signed-off-by: Kim Topley <ktopley@apple.com>

Author: ktopley-apple

PATCHES

@@ -505,3 +505,4 @@ github commits starting with 29bdc2f from
 [90a84a1] APPLIED rdar://54572081
 [7721660] APPLIED rdar://54572081
 [c5af10f] APPLIED rdar://54572081
+[f01432d] APPLIED rdar://54572081