Replace uses of String.isEmpty and Arrays.copyOf methods
(both introduced in java 6) with equivalent code that makes
use of only methods available in the java 5 runtime.
This allows the ADQL library, if cross-compiled for java 5,
to run without errors on a java 5 runtime.

[ADQL,TAP] Add STC-S and UDFs support in the ADQL parser. Now, it is possible to provide a list of allowed UDFs, regions and coordinate systems. The ServiceConnection of TAP is now able to provide these lists and to propagate them to the ADQLExecutor. UDFs and allowed regions are now listed automatically in the /capabilities resource of TAP. The type 'geometry' is now fully supported in ADQL. That's why the new function 'isGeometry()' has been added to all ADQLOperand extensions. Now the DBChecker is also able to check roughly types of columns and UDFs (unknown when parsing syntactically a query). The syntax of STC-S regions (expressed in the REGION function) are now checked by DBChecker. However, for the moment, geometries are not serialized in STC-S in the output....but it should be possible in some way in the next commit(s).

1/ let the function ROUND having 2 parameters
2/ wrap Operations (WrappedOperand) with brackets when there are brackets in the ADQL query

ADQL: Fix an ADQL bug (raised by Dave Morris) in the management of subqueries: before, it was impossible to use (in a clause different from the FROM) columns of a father query inside a subquery.