More URLs for the install chapter

Author: jimwins

entities/global.ent

@@ -110,6 +110,7 @@
 <!ENTITY url.gmagick.imagemagickdiff.faq "http://www.graphicsmagick.org/FAQ.html#how-does-graphicsmagick-differ-from-imagemagick">
 <!ENTITY url.gmp "http://gmplib.org/#DOWNLOAD">
 <!ENTITY url.gnochm "http://gnochm.sourceforge.net/">
+<!ENTITY url.gnu.autoconf "https://www.gnu.org/software/autoconf/autoconf.html">
 <!ENTITY url.gnu.configure "http://www.airs.com/ian/configure/">
 <!ENTITY url.gnu.make "https://www.gnu.org/software/make/make.html">
 <!ENTITY url.gnupg "http://www.gnupg.org/">
@@ -395,6 +396,7 @@
 <!ENTITY url.random.xoshiro "https://prng.di.unimi.it/">
 <!ENTITY url.random.gamma-section "https://dl.acm.org/doi/10.1145/3503512">
 <!ENTITY url.rar "http://www.rarlabs.com/">
+<!ENTITY url.re2c "https://re2c.org/">
 <!ENTITY url.readline "http://cnswww.cns.cwru.edu/~chet/readline/rltop.html">
 <!ENTITY url.readline.windows "http://mingweditline.sourceforge.net/">
 <!ENTITY url.recode "http://directory.fsf.org/All_GNU_Packages/recode.html">