MFC r248788 (erwin):

Update BIND to 9.8.4-P2

Removed the check for regex.h in configure in order
to disable regex syntax checking, as it exposes
BIND to a critical flaw in libregex on some
platforms. [RT #32688]
MFC r248276:
Rewrite the vfs_bio_clrbuf(9) to not access the b_data for B_VMIO
buffers directly, use pmap_zero_page_area(9) for each zeroing page
region instead.
MFC r248277:
Remove excessive and inconsistent initializers for the various kernel
maps and submaps.