Log Message:
pkgtools/pkglint: update to 5.6.7

Changes since 5.6.6:

User-defined variables that are not yet added to BUILD_DEFS are only
reported once per file.

Unnecessary space after variable names is only worth a note instead of
a warning. Example:

        MASTER_SITES =  https://cdn.example.org/

All variable names that are defined in the pkgsrc infrastructure are
assumed to be available to the package Makefiles. This reduces the
number of wrong "used but not defined" warnings, at the expense of

Variable names that are used in other variable names are checked
whether they are defined somewhere. Example:

        CFLAGS+=        ${CFLAGS.${PARAM}}      # PARAM is now checked

In SUBST_SED, when the pattern is s,@VAR@,${VAR}, or a slight variant
thereof, pkglint suggests to define SUBST_VARS instead, which frees the
package author from thinking about how to escape special characters and
is generally easier to read. Example:

        SUBST_SED.class=        s,@VAR@,${VAR:Q},

        SUBST_VARS.class=       VAR

Directives like .if !defined(...) are now handled the same whether or
not there is a space after before the (...).

The check for locally modified files now works independently of the
timezone.

As always, lots of refactorings have happened under the hood. Many small
bugs have been discovered and fixed accordingly.