Don't specify the `-std` flag in Makefile or re2.pc.

As Frank Heckenbach notes in https://bugs.debian.org/1003482:

> re2.pc contains "-std=c++11". This conflicts with other "-std"
> options, especially if one wants to use a newer standard (which
> otherwise works with libre2, as indicated by its support for
> string_view, e.g.).
>
> In order to make sure it's used only with C++11 or newer, you may
> want to check __cplusplus in the header instead.

As gcc and clang default to C++ standards greater than 11, these days,
we can use with the default, rather than the older standard.

Fixes #352.

Change-Id: I1b078df54f583e0b980e1b6341c6d401c8c9d937
Reviewed-on: https://code-review.googlesource.com/c/re2/+/59570
Reviewed-by: Paul Wankadia <junyer@google.com>
2 files changed