Improve reporting, mostly around type information but also source spans

[dorchard]

This PR does two things:

1. Improves the reporting of type information, e.g.
   previously we'd get things like:

_area_of_circle_1                - Function
area_of_circle_area_2           Real 4 Variable
area_of_circle_pi_4             Real 4 Parameter
area_of_circle_r_3              Real 4 Variable
main_area_6             Real 4 Variable
main_r_5                Real 4 Variable

now we get:

4:12     r              Real 4 Variable
4:15     area           Real 4 Variable
11:4     area_of_circle          - Function
12:27    pi             Real 4 Parameter
13:28    r              Real 4 Variable
14:16    area           Real 4 Variable

2. This PR deals with the long standing issues that source span column numbers are always 1 bigger than they should be! This is now fixed in the Show instance (as fixing it deeper down causes issues with the way the lexer automata works).