Unable to print exceptions of unicode identifiers
I suspect this is windows specific but I'm not certain (I couldn't reproduce it with an older ghc on osx).
Here is an example of the problem:
```
$ ghcii.sh
GHCi, version 7.6.1: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude λ> ⇒
<interactive>:2:1: parse error on input `*** Exception: <stderr>: hPutChar: invalid argument (invalid character)
```
On other platforms the message looks more like: parse error on input \`=\>'
(not the automatic translation from ⇒ to =\>, I think that's a separate bug related to the unicode symbols extension)
On windows my ghc is version 7.6.1. On OSX (where I could NOT reproduce the exception), my ghc is 7.4.1. I don't know if the GHC version matters. I strongly suspect this is a windows unicode issue.
GHC gives similar behavior to ghci, for example on this input:
```
⇒ = 1
```
ghc tries to give an error message but throws an exception printing ⇒.
<details><summary>Trac metadata</summary>
| Trac field | Value |
| ---------------------- | ------------ |
| Version | 7.6.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture | |
</details>
<!-- {"blocked_by":[],"summary":"Unable to print exceptions of unicode identifiers","status":"New","operating_system":"","component":"Compiler","related":[],"milestone":"","resolution":"Unresolved","owner":{"tag":"Unowned"},"version":"7.6.1","keywords":[],"differentials":[],"test_case":"","architecture":"","cc":[""],"type":"Bug","description":"I suspect this is windows specific but I'm not certain (I couldn't reproduce it with an older ghc on osx).\r\n\r\nHere is an example of the problem:\r\n{{{\r\n$ ghcii.sh\r\nGHCi, version 7.6.1: http://www.haskell.org/ghc/ :? for help\r\nLoading package ghc-prim ... linking ... done.\r\nLoading package integer-gmp ... linking ... done.\r\nLoading package base ... linking ... done.\r\nPrelude λ> ⇒\r\n\r\n<interactive>:2:1: parse error on input `*** Exception: <stderr>: hPutChar: invalid argument (invalid character)\r\n}}}\r\n\r\nOn other platforms the message looks more like: parse error on input `=>'\r\n\r\n(not the automatic translation from ⇒ to =>, I think that's a separate bug related to the unicode symbols extension)\r\n\r\nOn windows my ghc is version 7.6.1. On OSX (where I could NOT reproduce the exception), my ghc is 7.4.1. I don't know if the GHC version matters. I strongly suspect this is a windows unicode issue.\r\n\r\nGHC gives similar behavior to ghci, for example on this input:\r\n{{{\r\n⇒ = 1\r\n}}}\r\n\r\nghc tries to give an error message but throws an exception printing ⇒.","type_of_failure":"OtherFailure","blocking":[]} -->
issue