GNU C++ library stylistic conventions

• C++ source files have file extension `.cc'. Both C-compatibility header files and class declaration files have extension `.h'.
• C++ class names begin with capital letters, except for istream and ostream, for AT&T C++ compatibility. Multi-word class names capitalize each word, with no underscore separation.
• Include files that define C++ classes begin with capital letters (as do the names of the classes themselves). `stream.h' is uncapitalized for AT&T C++ compatibility.
• Include files that supply function prototypes for other C functions (system calls and libraries) are all lower case.
• All include files define a preprocessor variable _X_h, where X is the name of the file, and conditionally compile only if this has not been already defined. The #pragma once facility is also used to avoid re-inclusion.
• Structures and objects that must be publicly defined, but are not intended for public use have names beginning with an underscore. (for example, the _Srep struct, which is used only by the String and SubString classes.)
• The underscore is used to separate components of long function names,
  e.g., set_File_exception_handler().
• When a function could be usefully defined either as a member or a friend, it is generally a member if it modifies and/or returns itself, else it is a friend. There are cases where naturalness of expression wins out over this rule.
• Class declaration files are formatted so that it is easy to quickly check them to determine function names, parameters, and so on. Because of the different kinds of things that may appear in class declarations, there is no perfect way to do this. Any suggestions on developing a common class declaration formatting style are welcome.
• All classes use the same simple error (exception) handling strategy. Almost every class has a member function named error(char* msg) that invokes an associated error handler function via a pointer to that function, so that the error handling function may be reset by programmers. By default nearly all call *lib_error_handler, which prints the message and then aborts execution. This system is subject to change. In general, errors are assumed to be non-recoverable: Library classes do not include code that allows graceful continuation after exceptions.