Add fn:regex and fn:compiled-regex-record

[GuntherRademacher]

These changes add support for the new fn:regex function and the built-in fn:compiled-regex-record type.

fn:regex is implemented by constructing a map of FuncItem closures over the constant pattern and flags. Each closure body is a fresh StandardFunc instance (FnMatches, FnTokenize, etc.). Prior to this change, each such instance had its own per-instance regex cache. The per-instance cache has been replaced by a single per-query cache on QueryContext, shared by all RegExFn instances within a query. The pattern compiled eagerly in fn:regex is therefore found immediately by any subsequent member function call - fulfilling the spec's intent of compiling once and reusing.

RegExpr, GroupInfo, and GroupScanner were moved from inner classes of RegExFn to a new top-level class org.basex.query.util.regex.RegExpr. This was done in order to avoid QueryContext depending on a type defined inside a concrete function implementation. The only code changes are visibility adjustments required by the package move: the class, its constructor, the pattern field, and the two accessor methods are now public (they were package-private, but callers in org.basex.query.func.fn and org.basex.query require access), algorithmic logic is identical.

This fixes QT4 tests

• Keywords-fn-regex-1
• fo-test-fn-regex-001
• fo-test-fn-regex-002
• fo-test-fn-regex-004

Additionally, a test has been added to verify that constructor functions exist for all built-in record types, and constructor functions have been added where they were missing.

[GuntherRademacher]

A deliberate deviation from the spec: the replace member of fn:compiled-regex-record is typed as xs:string rather than xs:string*. The spec's xs:string* seems incorrect, fn:replace always returns exactly one string. So the stricter type is used here accordingly. A remark about this has been added to qtspecs#2590.