astro/gnuastro: update GNU Astronomy Utilities to version 0.20

Reported by:	upstream maintainer (via information bulletin)

astro/gnuastro/Makefile

@@ -1,6 +1,5 @@
 PORTNAME=	gnuastro
-PORTVERSION=	0.19
-PORTREVISION=	2
+PORTVERSION=	0.20
 CATEGORIES=	astro
 MASTER_SITES=	GNU
 

astro/gnuastro/distinfo

@@ -1,3 +1,3 @@
-TIMESTAMP = 1666570568
-SHA256 (gnuastro-0.19.tar.lz) = 7f7510b3136dd8ff40c7255f7ba0d62d69ffdcb534390a1973bc3afa491c58a4
-SIZE (gnuastro-0.19.tar.lz) = 4475215
+TIMESTAMP = 1682799210
+SHA256 (gnuastro-0.20.tar.lz) = 56404a4b919e106742d74d9ce77402413c595b3da088272a98a9abd541537315
+SIZE (gnuastro-0.20.tar.lz) = 4600460

astro/gnuastro/pkg-plist

@@ -20,6 +20,7 @@ bin/astscript-psf-subtract
 bin/astscript-psf-unite
 bin/astscript-radial-profile
 bin/astscript-sort-by-night
+bin/astscript-zeropoint
 bin/astsegment
 bin/aststatistics
 bin/asttable
@@ -85,12 +86,12 @@ include/gnuastro/warp.h
 include/gnuastro/wcs.h
 lib/libgnuastro.a
 lib/libgnuastro.so
-lib/libgnuastro.so.17
-lib/libgnuastro.so.17.0.0
+lib/libgnuastro.so.18
+lib/libgnuastro.so.18.0.0
 lib/libgnuastro_make.a
 lib/libgnuastro_make.so
-lib/libgnuastro_make.so.17
-lib/libgnuastro_make.so.17.0.0
+lib/libgnuastro_make.so.18
+lib/libgnuastro_make.so.18.0.0
 libdata/pkgconfig/gnuastro.pc
 man/man1/astarithmetic.1.gz
 man/man1/astbuildprog.1.gz
@@ -114,6 +115,7 @@ man/man1/astscript-psf-subtract.1.gz
 man/man1/astscript-psf-unite.1.gz
 man/man1/astscript-radial-profile.1.gz
 man/man1/astscript-sort-by-night.1.gz
+man/man1/astscript-zeropoint.1.gz
 man/man1/astsegment.1.gz
 man/man1/aststatistics.1.gz
 man/man1/asttable.1.gz
@@ -149,3 +151,4 @@ share/info/gnuastro-figures/sphereandplane.png
 share/info/gnuastro-figures/sphereandplane.txt
 %%DATADIR%%/astscript-fits-view.desktop
 %%DATADIR%%/completion.bash
+%%DATADIR%%/zeropoint.mk