Fix misaligned match results with perl backend

Consider this source text:
```
98.249.190.144 - - [19/Jul/2012:20:33:04 +0200] "GET /news/8603-exclusive-jack-johnson\xD3sets2.looktothestars.org/photo/1303-oxfam/tiny_square.jpg?1263992329 HTTP/1.1" 404 322 "http://www.looktothestars.org/?lang=it" "Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)"
98.249.190.144 - - [19/Jul/2012:20:33:04 +0200] "GET /cause/5-educat-tweet HTTP/1.1" 301 113 "http://www.looktothestars.org/?lang=en" "Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)"
98.249.190.144 - - [19/Jul/2012:20:33:04 +0200] "GET /2064 HTTP/1.1" 404 322 "http://www.looktothestars.org/?lang=hu" "Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)"
98.249.190.144 - - [19/Jul/2012:20:33:04 +0200] "GET /news/2601-dionne-warwicisteneradata, HTTP/1.1" 301 154 "http://www.facebook.com/plugins/like.php?href=http://www.looktothestars.org/news/2601-dionne-warwick-and-sinbad-headline-charity-event&send=false&layout=button_count&width=125&show_faces=false&action=recommend&colorscheme=light&font&height=21" "Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)"
98.249.190.144 - - [19/Jul/2012:20:33:04 +0200] "GET /celebrity/tweet HTTP/1.1" 404 9 "http://www.looktothestars.org/?lang=fil" "Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)"
```

and the regex:

```
(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}) \S+ \S+ \[.*?\] "GET [^? ]*(?:\\x|\/\.\.?\/|[=,:\}\{\(\)])\S*? HTTP\/1\.1"
```

The second highlighted match (on line 4) does not match the beginning of the line. When matching in a large text, the highlighted matches become progressively more misaligned as one moves later in the text.

This commit fixes the issue.
Escape quotes and matched backslashes in perl match results

When matching text containing backslashes, e.g. "\n", the "Group" output will display this as a newline. To prevent this, we have perl escape any backslashes in the group output so that 'read will handle the expression correctly.

Further, if the matched text contains double quotes, the resulting sexp printed by the perl program is invalid, and so the `*Groups*` buffer is empty. This commit also fixes this second issue.
Merge pull request #2 from purcell/patch-2

Escape quotes and matched backslashes in perl match results
Merge pull request #1 from purcell/patch-1

Fix misaligned match results with perl backend