implemented VARPTR for string arrays
Docstrings for StringPtr
var.py: docstrings and minor code cleanup
Added note for oddly placed fre() and program_memory_size()
Whitespace error in string_ptr.
moved string buffers to a string list with memory addresses as keys. Breaks FIELD for now.
check memory and garbage before storing variables
adapted collect_garbage to new string storage
implemented VARPTR for FIELD variables
Simplified & corrected FIELD variable handling with VARPTR
MID$ statement fixes; FIELD, MID$, LSET now accept string array arguments
added FCB description
Don't store empty strings in string table (avoids duplicate keys)
moved field_mem_start and field_mem_offset to var.py to fix circular dependency issues
fixed collect_garbage's mangling of string arrays
fix old iolayer references to field_mem variables in var.py
fix old iolayer references to field_mem variables in machine.py
fix incorrect error class: Runerror -> RunError
Add test for FIELD, LSET and SWAP using strings and string arrays