Improve error message for redefinitions

[gradha]

Given the file variable_leaks.nim:

include evil_leak

when isMainModule:
  let
    some_var = 2

And the file evil_leak.nim:

const
  SOME_VAR = "some var"

The compiler produces the following output:

$ nimrod c variable_leaks.nim 
variable_leaks.nim(5, 12) Error: redefinition of 'some_var'

It would help if the redefinition error could also point to the file/line where the original definition is, since a naive case sensitive grep would not find the source of the problem.

[Araq]

Still an issue.

[data-man]

Still an issue.

Not reproduced on devel.

include evil_leak

echo SOME_VAR

when isMainModule:
  let
    some_var = 2

  echo some_var

[timotheecour]

@data-man what do you mean "Not reproduced on devel." ? see #8581

[data-man]

@timotheecour

I mean that variable_leaks.nim(5, 12) Error: redefinition of 'some_var don't appears for me.
Now outputs:

some var
2

[Araq]

@data-man Yeah, the example is outdated but the issue is real.