Get wrong value for nagative number with decimal point

```
What steps will reproduce the problem?
1.put -100000.1 into cell
2.read it
3.the result is 10637418.1

What is the expected output? What do you see instead?

Please provide any additional information below.
If I put -10000.1 or the number don't have a decimal point, the result is OK.
The problem does only happen when the number have a decimal point and the total
digital is more than 7.
Please have a look at this issue. Thanks.
```

Original issue reported on code.google.com by `Ruinan....@gmail.com` on 5 Feb 2012 at 5:34

Start by reproducing the reported case in the PHP Excel reader: enter -100000.1 in a cell and compare the returned value with cases using fewer digits, no decimal point, and a positive value. Done means negative decimal values with more than seven total digits are read without changing their value; the issue names no file or test to run.

Written by the indexing model from the issue text.