Avoid the need for the user to specify MACHINE

[Eyal Rozenberg]

CMake should be able to provide sufficient information regarding the platform on which we're building so as to obviate the need for setting the MACHINE parameter. Right now,

At the moment, the effects of MACHINE are:

1. Choosing between sets of preprocessor defines in config.h:

#define _INCLUDE_POSIX_SOURCE /* or not define it */
#define STDLIB_HAS_GETOPT /* or not define it */
#define SUPPORT_64BITS /* or not define it */
#define DSS_HUGE long
#define HUGE_COUNT 2
#define HUGE_FORMAT "%ld"
#define HUGE_DATE_FORMAT "%02lld"
#define RNG_C 1ull
#define RNG_A 6364136223846793005ul

2. Some code in config.hand driver.ci is conditioned ondefined(POSIX)||!defined(WIN32))- mostly relating to working with process id's and signals, and related#include`s.
4. Path separator definition
5. Use of an MS Visual Studio intrinsic instead of strdup() - for some really old version of MSVC

Also, it seems WIN32 is linked to the use of DATABASE=SQLSERVER for some reason

5. Some WIN32-specific optimizations under WIN32_Lean-and-Mean

... have I missed something?