Add back get_uinteger for boolean_type.

This was removed in ed0b19b94bf07056b5e0cfe64d4d05c3ebae801a

Change-Id: I548ca955eda6e0b6991a0f6731cbbb3bf82e0e2b
Reviewed-on: https://code.wireshark.org/review/4620
Reviewed-by: Stig Bjørlykke <stig@bjorlykke.org>
Tested-by: Stig Bjørlykke <stig@bjorlykke.org>