mesa: Use quotes on bool driconf options to prevent stdbool.h breakage.

mesa: Use quotes on bool driconf options to prevent stdbool.h breakage.

Since stdbool.h's "true" and "false" are #defines, they got expanded when
used as macro arguments, and that expanded value was stored in the
XML string, producing XML that driconf would then fail to parse.

Currently no drivers included stdbool along with driconf, but I keep
accidentally doing so on intel as we move towards using normal C.

v2: rebase on master.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org> (v1)