Added lib/healpix

Makefile.am

configure.ac

src/Makefile.am

src/lib/healpix/Makefile.am

src/lib/healpix/README.md

src/lib/healpix/an-bool.h

src/lib/healpix/bl-nl.c

src/lib/healpix/bl-nl.h

src/lib/healpix/bl-nl.inc

src/lib/healpix/bl-nl.ph

src/lib/healpix/bl.c

src/lib/healpix/bl.h

src/lib/healpix/bl.inc

src/lib/healpix/bl.ph

src/lib/healpix/healpix-utils.c

src/lib/healpix/healpix-utils.h

src/lib/healpix/healpix.c

src/lib/healpix/healpix.h

src/lib/healpix/keywords.h

src/lib/healpix/mathutil.c