Support for OS X.

Following changes were made:
a) Incremented the BUILDNUM in the Makefile.
b) Added "<inttypes.h> for proper formatting of UINT64 datatype.
c) Added the function mempcpy if it is not defined (since mempcpy is a GNU extension).
d) "sig_t" is defined in /usr/include/signal.h for BSD variants, so changed the typedef to sgn_t.
e) Changed the printf statements for UINT64 to get rid of compiler warnings.