filter_create_ext() is documented to take a NULL terminated set of
arguments. 0 is promoted to an int so this would fail on 64-bit
systems if the value was not passed in a register. On all currently
supported 64-bit architectures it is.
Obtained from: CheriBSD
Sponsored by: DARPA, AFRL
r124183: Work around a `label defined but not used' warning.
r179549: De-register declarations.
r179657: De-register declarations in non-dot-c files.
r181269: Mark yy_fatal_error() as __dead2.
r228992: Spelling fixes.
r240518: Correct double "the the".
