Hi,

the attached patch implements pretty printers relevant for iteration
over std::vector<bool>, thus handling the TODO
added in commit 36d0dada6773d7fd7c5ace64c90e723930a3b81e
("Have std::vector printer's iterator return bool for vector<bool>",
2019-06-19):

    TODO add printer for vector<bool>'s _Bit_iterator and
_Bit_const_iterator

Tested on x86_64-pc-linux-gnu (Debian testing).

I haven't filed any copyright assignment for GCC yet, but I'm happy to
do so when pointed to the right place.

Best regards,
Michael