v0.0.4

Language enhancements/fixes:

• Functions can be forward declared.
• Structures members can reference themselves (e.g. for trees, linked lists etc).
• Fixed debugger variable display when inside an overloaded function (was looking up the wrong overload sometimes).

New library functions:

• `split` - Splits a string by a delimiter.
• `trimstart`, `trimend`, `trim` - Trim whitespace from the start and/or end of a string.
• `toint`, `tofloat` - Convert string to int/float.
• `loadtext` - Load a text file into a string.
• `fileexists` - Check whether a file exists.