feat: Added possiblity to clone expressions (both AST node + tokenstream) (#268)

* feat: Added possiblity to clone expressions (both AST node + tokenstream)

This will make it easier to create copies out of existing expressions
without having to rebuild them yourself manually (especially if their
structure is not fixed).

* feat: Added cloning of regexes

* fix: Fixed Python bindings build

* tests: Added Python bindings clone tests (very limited for now)

* fix: regex parsing with \/

* fix: Fixed print in Dump Rules AST example for RegexpText visitor

* fix: Fixed (finally) parser for regexes and their escape sequences

* fix: Fixed Python type hints

Author: metthal

include/yaramod/types/expression.h

@@ -83,6 +83,7 @@ class Expression
 	}
 	virtual TokenIt getFirstTokenIt() const = 0;
 	virtual TokenIt getLastTokenIt() const = 0;
+	virtual Expression::Ptr clone(const std::shared_ptr<TokenStream>& /*target*/) const = 0;
 	/// @}