Log Message:
sysutils/qlogtools: skip nonexistent error.h when fixing errno

Some packages using mk/djbware.mk do not have error.h but need to fix the
errno declaration in other files.  Up to now, there was no good way of
achieving exactly this.

Building packages like these in a SUBST_NOOP_OK=no build makes these
packages fail.  To fix these packages, the configuration of the files
needed to be a bit more flexible.