Bug 1009101 Part 1: Enable building moz_pkix on its own to produce a shlib.

  - The shared library is "mozpkix".
  - Renamed "pkix/Time.h" to "pkix/pkixtime.h" to avoid shadowing <time.h>
    when building as a standalone project.
Bug 1009101 Part 2: Scaffolding to support linking in mozpkix.

 - Added "mozpkixnss" library to NSS as C++ code that is extern C.
 - Added dependency on "mozpkix"
 - Added SQLITE_USE_SYSTEM option to NSS to sidestep an OSX Mavericks build
   conflict with the builtin sqlite library. If this is a problem for people
   other than me, it should go into the build options for mavericks and above.