The two different variants of the threadlib basically are
win32 and unix - use _WIN32 to check for this consistently,
instead of occasionally using __GNUC__ to enable the unix
codepath. (__GNUC__ is also defined on mingw, which still is
a windows platform and should use the _WIN32 code.)
When adding the (dwMilliseconds % 1000) * 1000000 part
to ts.tv_nsec, the ts.tv_nsec field can grow larger than one
whole second. Therefore first add all of dwMilliseconds to
the tv_nsec field and add all whole seconds to the tv_sec
field instead - this way we make sure that the tv_nsec field
actually is less than a second.
Also use the __APPLE__ predefined define instead of MACOS for enabling
these code paths.
This also avoids having to link to the CoreServices framework in
order to get the Gestalt function.
This gets rid of the code that parses /proc/cpuinfo, and avoids
forking within the library.
The previous code also failed build on modern glibc versions
due to ignoring the return value of the system, read and write
system calls.
