fix optgroup formatting for Firefox. Use `@input-height-base` in `.navbar-vertical-align()` for `.navbar-form`

BS3 commits 35573db and 0c167a1
round line-height-computed up instead of down to get 20px
Use `@input-height-base` in `.navbar-vertical-align()` for `.navbar-form`

BS3 commit 0c167a1