[PATCH 0/3] MR7415: findstr should default to regex search.

[eric pouech (＠epo)]

Our findstr implementation defaults to textual search, while native
defaults to regex.
So this MR:
- add tests to show that,
- reverts the default,
- adapt tests that were written with textual search in mind to pass textual
  search option

Note: native fails when passing the two flags ('findstr /l /r...'). I didn't bother
fixing our implementation.