Provide defines for build-time (header) version checks

Currently building L0 programs give "mystery" errors if system L0 headers are not new enough.

It would be much user-friendlier if ze_api.h would include defines that can be used to check whether L0 headers are new enough, and which are (automatically) updated on every release.

E.g. with something like this:

#define L0_HEADER_MAJOR 1
#define L0_HEADER_MINOR 9
#define L0_HEADER_PATCHLEVEL 9
#define L0_HEADER_VERSION (L0_HEADER_MAJOR * 10000 + L0_HEADER_MINOR * 100  + L0_HEADER_PATCHLEVEL)

Code could then give much better error:

# if L0_HEADER_VERSION < 10909
#  error "At least version v1.9.9 of the L0 header(s) required"
#endif

(L0_HEADER_VERSION obviously assumes that project does not use more than 99 minor & patchlevel versions.)

PS. This is needed because doing package / pkg-config version check is not enough for all cases. Even if system would have new enough version installed from distro packages, code could e.g. be getting some older version from /usr/local/include. Or user could be directly compiling C/C++ files for self-contained L0 utilities.

The requested change is centered on ze_api.h; start by reviewing the header's existing version information and the release process that updates it. Add build-time version defines usable by C/C++ consumers, and verify that older headers can be distinguished from the minimum version required by a program.