bash lexer: don't include final newline in single line comments.

[emanuele6]

Since the final newline character was included in Comment.Single, code blocks that ended in a comment like the following

{{{#!highlight bash
echo hello # this command writes "hello" to stdout
}}}

were getting an extra line at the end.

Using a lookhead assertion instead of matching \n literally fixed the issue.

---

before applying this patch:

after applying this patch:

[emanuele6]

I have noticed that this also needs to be changed in the regular expression for Comment.Hashbang; otherwise, the following code block still gets an extra newline:

{{{#!highlight bash
#!/bin/bash
}}}

[ThomasWaldmann]

This file is from the pygments project.

As most other files in the support directory, we just use them "as is". Any changes / fixes have to be done upstream, so please contribute this to the pygments FOSS project.