- make sortdeps() working with dependency lists containing one or no elements;
- provide protection against incorrect input (dependency list).

- use strlcpy(3) instead of strcpy(3) to copy user-supplied argument into a
  fixed size buffer;
- make `-t' flag in pkg_*(1) tools actually working.

versioning.

- fix harmless compiler's warnings;
- before refusing to delete package because "there are packages installed
  that require this package" check that packages in question is actually
  installed;
- add new `-r' option to pkg_delete(8), which instructs it to delete not only
  packages specified at command line, but all packages that depend on
  specified packages as well.

This brings in the following deltas:

  1.57      src/usr.sbin/pkg_install/create/perform.c
  1.7       src/usr.sbin/pkg_install/delete/delete.h
  1.23      src/usr.sbin/pkg_install/delete/main.c
  1.33      src/usr.sbin/pkg_install/delete/perform.c
  1.27      src/usr.sbin/pkg_install/delete/pkg_delete.1
  1.42      src/usr.sbin/pkg_install/info/perform.c
  1.4       src/usr.sbin/pkg_install/lib/deps.c
  1.38      src/usr.sbin/pkg_install/lib/lib.h

- kill blank lines at the end of lib/global.c;
- in the case of checksum mismatch print name of offending file to stderr;
- replace dozen instances of "(tmp = getenv(PKG_DBDIR) ? tmp : DEF_LOG_DIR)"
  with macro;
- exists(../../crypto) --> exists(${.CURDIR}/../../crypto) in a top-level
  Makefile.