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
d) "sig_t" is defined in /usr/include/signal.h, so changed the typedef to sgn_t
e) Changed the printf statements for UINT64 to pacify the compiler
This commit of samblaster 0.1.21 includes the following:

1) Fixed bug that resulted in intermittent incorrect detection of
   split-read mappings when using --acceptDupMarks option.
2) Merged in pull request from Aakrosh Ratan for OSX support,
   with additional minor mods to make Linux support more portable.
3) Updated SAMBLASTER_Supplemental.pdf to include final samblaster
   citation, and fixed recently broken link to the file in README.