Improve locations in ghci errors

This shows GHC complaining of an error in line 9 of a 7 line file. The error is really on line 4. My guess is it's adding the line within the :{ ... :} to the line of the :}, in which case the best fix is probably to remember the position of the :{ and set the line number to that when evaluating the expression.

Prelude> :! cat script_me
:{
let y1 = 1
    y2 = 2
    Y3 = 3
    y4 = 4
    y5 = 5
:}
Prelude> :! wc -l script_me
7 script_me
Prelude> :script script_me

script_me:9:5: Not in scope: data constructor `Y3'

Additionally, errors in .ghci files currently have <interactive> as their location. Probably sourceConfigFile in ghc/InteractiveUI.hs should set the filename.

Trac metadata

Trac field	Value
Version	7.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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