- 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.

     of add/mail.c

When creating package sort dependencies in dependency order rather than in the
order specified on the command line. This should allow ``pkg_add -r'' to
work seamlessly with packages created after this change.

Tested by:	bento
Approved by:	jkh

- globs/regexs in pkg_delete(1);
- interactive confirmation in pkg_delete(1);
- `-a' option for pkg_delete;

Sync up with following revisions:
src/usr.sbin/pkg_install/delete/delete.h	-> 1.6
src/usr.sbin/pkg_install/delete/main.c		-> 1.21
src/usr.sbin/pkg_install/delete/perform.c	-> 1.27
src/usr.sbin/pkg_install/delete/pkg_delete.1	-> 1.24
src/usr.sbin/pkg_install/info/info.h		-> 1.18
src/usr.sbin/pkg_install/info/perform.c		-> 1.36
src/usr.sbin/pkg_install/lib/Makefile		-> 1.7
src/usr.sbin/pkg_install/lib/lib.h		-> 1.32

Fix a typo, that in some cases may lead to incorrect packages reordering.