re2c: upgrade 3.0 -> 3.1

re2c: upgrade 3.0 -> 3.1

Changelog:
==========
- Added capturing groups with leftmost greedy semantics:
- Added non-capturing groups:
- Regenerated Unicode include header to support a newer standard
- Published TDFA paper: https://arxiv.org/abs/2206.01398, co-authored with
  Angelo Borsotti
- Removed experimental algorithms that are superseded by TDFA(1) and
  generally less efficient:
- Fixed parsing of raw UTF-8 characters in Flex compatibility mode
- Added header file to the dependencies generated with "--depfile" option
- Fixed stack overflow on large regular expressions by rewriting recursive
    functions in iterative form and limited stack to 256K on GithubActions CI
- Added minimal http://bazel.build integration
- Added configure option "--enable-parsers" that regenerates bison parsers
- Added CMake option "RE2C_REBUILD_PARSERS"
- Moved the entire codebase to C++11.
- Added uniform error handling (return codes are now properly checked and
 returned to the caller).
- Reorganized codegen subsystem in four well-defined phases (analyze,
 generate, fixup, render) and separated codegen from parsing phase.
- Improved memory allocation by using slab allocators instead of global free
 lists.
- Moved to pure API for bison parsers.
- Unified code style.
- Added "--verbose" flag to run_tests.py and suppressed verbose output by
 default.
- Multiple improvements of continuous testing with GithubActions.

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>