(Support) Generalized ROSE's database support

The sqlite3x interface is still present, but I've added an SqlDatabase
namespace with classes that are abstract enough to handle a variety
of relational database systems.  We currently support SQLite3 (via
sqlite3x classes copied into ROSE previously), and PostgreSQL (via
libpqxx detected during configure).

I've rolled this new SqlDatabase class because I wasn't able to
find an existing solution that's C++ oriented.
(Support) Added a linear congruential generator

The C library's rand() functions are not sufficient when one wants to
be able to have multiple independent sequences of pseudo-random
numbers.  I've added a LinearCongruentialGenerator class to ROSE.
(Support) Added a Combinatorics namespace and a couple functions

New functions:
  factorial()		computes factorial of N
  permute()		permutes a vector in place
(Support) Better error handling and debugging in SqlDatabase
(Support) SqlDatabase::Statement::bind() can be chained

Changed the return type of bind() so that they can be
chained together, as in:

  transaction->statement("insert into foo (c1, c2) values (?,?)")
      ->bind(0, c1)
      ->bind(1, c2)
      ->execute();
(Support) Expose the SQL-string escaping function in the API
(Support) Added base64 encode/decode functions to StringUtility
(Support) Added more functions to SqlDatabase

* Connection::openspec
* Transaction::connection
* Statement::transaction
(Support) Added missing #include
(Support) Better initialization for random numbers
(Support) Bulk loading for SqlDatabase; more exception handling
(Support) Added string-joining functions to StringUtility

The existing listToString functions were insufficient for my needs
and changing them would have broken API compatibility. I've added
join(), which is more like the Perl "join" function.
(Clone Detection) Checkpoint for major rewrite

The big CloneDetection.C program has been split in many smaller
commands, all of which allow run-time selection of either Sqlite3
or PostgreSQL, and all of which support incremental building of the
database.