This enables selected things from -Wextra, can't use -Wextra because it is
fussy enough to complain about unused params on functions... they are
there for a reason.
-Wsign-compare
-Wignored-qualifiers
not -Wimplicit-fallthrough=3 ... only on gcc 7
-Wtype-limits
-Wuninitialized
not -Wclobbered ... only on gcc 7ish
fix the warnings everywhere they were found.
- introduce lib/tls/mbedtls lib/tls/openssl
- move wrapper into lib/tls/mbedtls/wrapper
- introduce private helpers to hide backend
This patch doesn't replace or remove the wrapper, it moves it
to lib/tls/mbedtls/wrapper.
But it should be now that the ONLY functions directly consuming
wrapper apis are isolated in
- lib/tls/mbedtls/client.c (180 lines)
- lib/tls/mbedtls/server.c (317 lines)
- lib/tls/mbedtls/ssl.c (325 lines)
In particular there are no uses of openssl or mbedtls-related
constants outside of ./lib/tls any more.
