Add records and data types

[duncanamps]

Add records and data types.

Data types, whereas we have DB, DW etc. to make these more "debugger useful", specifically:

Data type	Bytes	Notes
char	1
byte	1	Unsigned
shortint	2
word	2
longint	4
dword	4
int64	8
qword	8

Records allow a definition something like:

DEFINE RECORD recname
rsize: word
signature: dword
entries: shortint
marker: char
csc: dword
end

And variables could be declared and used with:

RECORD buffer: recname
LD A,buffer.marker

Some things to think about.

• General grammar to make sure it doesn't mess everything else up
• Pointers to records
• Using this as a stack frame