RetroBASIC v1.1.0

This is the first fully-functional version of RetroBASIC, which should correctly run all BASIC Computer Games and More BASIC Computer Games, which are used as the reference implementations. The major improvement over v1.0.0 is the correct functioning of user-defined functions, DEF FN.

It also adds a number of extensions gathered from other BASIC dialects, notably a version of string slicing seen in the HP-a-like's including Apple, Atari, Sinclair, etc. The normal style is that of ANSI Full BASIC, A$(4:10), the colon indicating this is a slice and not array access. This allows it to slice strings stored in an array, a major advantage over the HP style. The HP/Apple/Atari style, A$(1,5), can be used with the --slicing option.

This version retains the dependency on GLib.