use line-height to compute margin for radios & checkboxes

Created by: AlexErmer

If you change the default settings which affect the lineheights, the radios and checkboxs aren't aligned properly to its labels. With this change, a dynamic is added to fix this issue.

Its not that pretty, because I have to use 13px as a default height for checkbox and radios (which applies at least to current FF and Chrome versions). Maybe anyone has a better solution for that?

Examples

here are some example screenshots to show the issue and the solution:

first the unchanged default

here the default with the fix: remains almost unchanged

now an example with @font-size-base: 20px; and @line-height-base: 1.828571429;

and here with my fix

and again with small with @font-size-base: 10px; and @line-height-base: 1.228571429;

and with the fix