Add fgrep to user space

[rnayakusf]

fgrep matches a fixed string against a stream and prints the lines that match. If only given one argument (the fixed string), it matches against standard input. Else, the other arguments are treated as files to match against, and fgrep will prepend the file path (relative to the current directory) and line number.

Alternatively, if the -R flag is passed, the additional arguments are treated as directories and will be recursively searched through for files to match against. Symlinks should be followed.

The -v flag inverts the selection, printing lines that don't match the string.

Libc changes:

• Add strstr

Future Development:

• Deal with symlink loops causing infinite recursion.
• Match against regex (grep).
• Color

[malensek]

One thing to consider is adding this functionality to the existing grep utility. On many modern systems running fgrep will get translated to grep -F, so perhaps you could add these features to the existing grep. I like the plan to add color, perhaps you could also add an option to print the matching file (since you will support multiple files)?