diff-options.txt: avoid "regex" overload in example

When we exemplify the difference between `-G` and `-S` (using
`--pickaxe-regex`), we do so using an example diff and git-diff
invocation involving "regexec", "regexp", "regmatch", ...

The example is correct, but we can make it easier to untangle by
avoiding writing "regex.*" unless it's really needed to make our point.

Use some made-up, non-regexy words instead.

Reported-by: Adam Dinwoodie <adam@dinwoodie.org>
Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/diff-options.txt

@@ -567,13 +567,13 @@ To illustrate the difference between `-S<regex> --pickaxe-regex` and
 file:
 +
 ----
-+    return !regexec(regexp, two->ptr, 1, &regmatch, 0);
++    return frotz(nitfol, two->ptr, 1, 0);
 ...
--    hit = !regexec(regexp, mf2.ptr, 1, &regmatch, 0);
+-    hit = frotz(nitfol, mf2.ptr, 1, 0);
 ----
 +
-While `git log -G"regexec\(regexp"` will show this commit, `git log
+While `git log -G"frotz\(nitfol"` will show this commit, `git log
--S"regexec\(regexp" --pickaxe-regex` will not (because the number of
+-S"frotz\(nitfol" --pickaxe-regex` will not (because the number of
 occurrences of that string did not change).
 +
 Unless `--text` is supplied patches of binary files without a textconv