Files containing ascii8 are not indexed (feature/request)

```
What steps will reproduce the problem?
1. File containing: PAT and ä (0xE4, a umlaut), ö (0xF6,o umlaut), other high
bit ascii chars
2. cindex -reset .
3. csearch -i PAT

What is the expected output? What do you see instead?
Expected to find PAT. Instead no match.

What version of the product are you using? On what operating system?
codesearch-0.01-windows-amd64.zip

Please provide any additional information below.
I looked at the source (write.go) and it seems to expect that files are in
UTF-8 only (this is a Go specification?). However it would be nice if csearch
could be used with any source files, including those with high bit ascii
characters. Or that there would be a command line option for this.

```

Original issue reported on code.google.com by `kilve...@gmail.com` on 21 Nov 2012 at 7:24