em dash is not correctly handled in calculator

[Former user]

Originally reported on Google Code with ID 334

What steps will reproduce the problem?
1.  Paste the following in speedcrunch: 500 – 250  
2.  Press enter


What is the expected output? What do you see instead?
Expected Result = The invalid expression pop up message should display.
Actual Result = No error message is displayed and speedcrunch returns a
result of 500.

What version of the product are you using? On what operating system?
Speedcrunch 0.10.1 on Windows 7

Please provide any additional information below.
An em dash is a grammatical punctuation mark that Microsoft Word will
sometimes use to replace a minus sign.  It would be helpful if speedcrunch
would either treat it as a minus sign or return an error message.  I
believe that the em dash exists in the extended ascii table.

Reported by [e-mail] on 2010-04-06 17:28:26

[Former user]

``` If you need to contact me, can you reply to [e-mail] ```

Reported by `[e-mail]` on 2010-04-06 17:30:12

[Former user]

``` This is a duplicate of issue 330. We should probably add support for that character... ```

Reported by `helder.pereira.correia` on 2010-04-06 17:45:57

[Former user]

``` Invalid expression is now shown. ```

Reported by `helder.pereira.correia` on 2011-12-05 23:16:40 - Status changed: `Fixed` - Labels added: Type-Defect, OpSys-All, Priority-High, Milestone-0.11