re2c: upgrade to 4.3

re2c: upgrade to 4.3

It introduces new features, improvements, and bug fixes, including
- a new code generation model using recursive functions
- new block types
- improved compile-time performance

It also adds a new warning, -Wdeprecated-eof-rule, and improves
the handling of the end-of-input rule

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>