build: enable extra warnings with meson

build: enable extra warnings with meson

While meson always adds -Wall flag to C compiles, the make build adds extra
warning flags that are not present in the meson build. This addresses that
shortcoming by adding additional warning flags to our builds. The one
omission is the -Wcast-align flag, which though present in make gcc builds,
gives a lot of warnings/errors when used with clang.

The removed warning "-Wunused-parameter" is covered by the "-Wextra"
parameter so is unnecessary.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Luca Boccassi <bluca@debian.org>