Allow sysconf to return CPU cache information

Allow sysconf to return CPU cache information

        * include/sys/unistd.h (_SC_LEVEL*): Add cache-related variables as
        on Linux.

        * fhandler_proc.cc (format_proc_cpuinfo): Fetch cache information
        from new cache functions in sysconf.cc, get_cpu_cache_intel and
        get_cpu_cache_amd.
        * sysconf.cc (__nt_query_system): New local helper.
        (get_nproc_values): Utilize __nt_query_system on pre-Windows 7 systems.
        Use GetLogicalProcessorInformationEx otherwise to handle more than
        64 CPUs.  Only handle _SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN.
        (get_phys_pages): New helper to handle _SC_PHYS_PAGES.
        (cpuid2_cache_descriptor): New array to map Intel CPUID 2 descriptor
        values to cache type, cache size, associativity and linesize.
        (cpuid2_cache_desc_compar): Comparision function for bsearch over
        cpuid2_cache_descriptor.
        (get_cpu_cache_intel_cpuid2): New function to fetch cache info from
        Intel CPUID 2.
        (get_cpu_cache_intel_cpuid4): Ditto from Intel CPUID 4.
        (get_cpu_cache_intel): New function as CPU-specific entry point.
        (assoc): New array to map associativity values from AMD CPUID
        0x80000006.
        (get_cpu_cache_amd): New function to fetch cache info from AMD CPUIDs
        0x80000005 and 0x80000006.
        (get_cpu_cache): New function to fetch cache info.
        (sca): Call get_phys_pages if _SC_PHYS_PAGES is requested.  Call
        get_cpu_cache for new _SC_* cache requests.
        (SC_MAX): Set to _SC_LEVEL4_CACHE_LINESIZE.
        (get_phys_pages(void)): Call get_phys_pages(int).
        * include/cygwin/version.h (CYGWIN_VERSION_API_MINOR): Bump.

        * new-features.xml (ov-new2.3): Document sysconf cache addition.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>