[sup-compat] Don't trim trailing whitespace on line introducing quotation.

[sup-compat] Don't trim trailing whitespace on line introducing quotation.

Ignoring this whitespace seems like a good idea to me, but it's
interfering with my comparisons with sup since sup doesn't do this.

This might be a commit worth dropping in the future since it exists
only for pedantic consistency with sup and not for any reason of its
own.