Use @font-size-small variable to calculate <small> font-size fixes #13713 #13809
Merge pull request #13882 from thomaswelton/issue-13713-use-variable-small

Use @font-size-small variable to calculate <small> font-size
grid class inconsistency 2

https://github.com/twbs/bootstrap/commit/32bde78e1996a92e6b801e1f4a475d5ab48685f8