toolchain: Add single arguments evaluation macros for min and max

MAX() and MIN() were evaluating arguments twice. If arguments are
functions they were called twice which resulted in bigger code
and potential misbehavior.

Added alternative macros (Z_MAX, Z_MIN) which can be used instead.
Macros have usage limitations thus they are not replacements. They
are also relying on GCC extension thus placed in gcc.h

Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>