Move library version number from configure.ac to libusb/version.h

Move library version number from configure.ac to libusb/version.h

This is neccessary to support native MS builds. The Windows resource
file libusb/libusb-1.0.rc must include the release version, which was
previously only available after configure had run and had substituted
the numbers into a generated libusb/libusb-1.0.rc file.

The version atoms are now stored as CPP style #defines in libusb/version.h
so that the .rc no longer needs to be generated but can simply include the
header file and access the version information directly.

The m4 macro LU_DEFINE_VERSION_ATOM() was added to configure.ac to get
version atoms from libusb/version.h for use in AC_INIT(). The macro
handles C and C++ style comments in version.h, but can easily be made
to fail by obscuring the file. Please don't do that.

Tested with MinGW using autoconf, and manual compile of libusb-1.0.rc
using RC.EXE Version 5.2.3690.0 from Visual C++ 2005 Express Edition.