SourceLayout: acl/, take 1

Moved src/ACL* and a few related files into src/acl/.
Renamed ACL source files from ACLFoo.{cc,cci,h} to Foo.{cc,cci,h}.

Added acl/ libraries, reorganized auth/ libraries, and split ACLChecklist
class to avoid circular dependencies among libraries.

Many targets in src/Makefile.am depended on selected ACL ACL*cc and related
sources.  These targets depend on acl/* libraries now. As a part of this
cleanup, the number of ufsdump sources went from about 160 to about 20.

No functionality changes were intended. Source code changes were kept to the
minimum. All my build tests are successful. However, since I had to move a lot
of files, move some code pieces, and split ACLChecklist, it is possible that
some targets will no longer build in some environments and some authentication
code will break.

Please see individual commit messages for details.