[ADQL] Support hexadecimal values (as numeric values).

src/adql/parser/grammar/ADQLGrammarBase.java

src/adql/parser/grammar/adqlGrammar201.jj

src/adql/query/operand/NumericConstant.java

src/adql/translator/JDBCTranslator.java

test/adql/parser/TestADQLParser.java

test/adql/translator/TestJDBCTranslator.java