C++ Binding: changes for version 1.3b

The following changes were made between versions 1.3a and 1.3b of the ZOOM C++ binding:

General Changes

1. Change char* to std::string everywhere: string objects are passed by reference when used as a method argument, are are non-const when returned from a method. Accordingly, add #include <string>
2. Change the return-type of all option-setting methods to a bool, indicating whether or not the option was recognised and therefore accepted.
   • This anticipates a forthcoming change to the ZOOM Abstract API.
3. Add some new comments, and clarify some existing ones.

Specific Changes

1. Remove the global option() functions.
2. Add a private copy-constructor and assignment operator to the connection class, thereby making connections uncopyable.
3. Add a default (no arguments) connection constructor which does not forge a network connection; accordingly, add a new connect() method, so that the connection may be forged after options have been set - for example, to allow server authentication parameters to be specified.
   • This anticipates a forthcoming change to the ZOOM Abstract API.
4. Add a private copy-constructor and assignment operator to the resultSet class, thereby making result sets uncopyable.
5. Remove getRecord() from the resultSet class: records are now retrieved by the record class's constructor.
6. Remove the clone() method from the record class. It was a wart that afforded some opportunity for optimisation; but clever reference-counting and suchlike will do that transparently.
7. Promote the record::syntax enumeration to a class: methods are provided to translate between the enumeration (enum value) and the record syntax name strings that must be passed into option().
8. Make the errcode() and errmsg() methods virtual in exception, as they should always have been; add a virtual destructor; remove the redundant redeclarations of the errmsg() method from the systemException and bib1Exception classes.
9. Add an extra systemException constructor with an explicit int code argument; the old one, which uses the value of the system errno, is also retained.
10. Change the name of the bib1Exception constructor's int argument from errcode to code, for consistency with other exception classes.