Import bsd.clang-analyze.mk based on NetBSD's version.

This allows 'make analyze' or 'make OBJ.clang-analyzer' to run the
Clang static analyzer and present results on stdout.

Obtained from: NetBSD (CVS Rev. 1.3)
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D5449