'large' is no longer a valid msdosfs mount option in head after r319735.

Removes the -o large passed to mount, when kdelibs-kde4 is built on
a recent-ish 12-CURRENT system. At the same time, fix a logic error
regarding the handling of the -L flag reported by HAL.

PR: 223125
Submitted by: rakuco
Reported by: avg
Approved by: tcberner (mentor, implicit)