[libpng17] Make autogen.sh work with automake 1.13 as well as 1.14. Do this

by always removing the 1.14 'compile' script but never checking for it.
diff --git a/ANNOUNCE b/ANNOUNCE
index a65865d..6572e0d 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -395,6 +395,8 @@
     useful side effect of avoiding a bogus warning generated by the latest
     version of the Intel C compiler (it objects to
     condition ? string-literal : string-literal).
+  Make autogen.sh work with automake 1.13 as well as 1.14. Do this by always
+    removing the 1.14 'compile' script but never checking for it.
 
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diff --git a/CHANGES b/CHANGES
index 181e443..b7a3c3a 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4684,6 +4684,8 @@
     useful side effect of avoiding a bogus warning generated by the latest
     version of the Intel C compiler (it objects to
     condition ? string-literal : string-literal).
+  Make autogen.sh work with automake 1.13 as well as 1.14. Do this by always
+    removing the 1.14 'compile' script but never checking for it.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/autogen.sh b/autogen.sh
index 6d674d9..ccbfad6 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -74,8 +74,11 @@
 #
 # The autotools generated files:
 libpng_autotools_files="Makefile.in aclocal.m4 config.guess config.h.in\
-   config.sub configure depcomp install-sh ltmain.sh missing test-driver\
-   compile"
+   config.sub configure depcomp install-sh ltmain.sh missing test-driver"
+#
+# Files generated by versions of configue >2.68 or automake >1.13 (i.e. later
+# versions than those reqiured by configure.ac):
+libpng_autotools_extra="compile"
 #
 # These are separate because 'maintainer-clean' does not remove them.
 libpng_libtool_files="scripts/libtool.m4 scripts/ltoptions.m4\
@@ -95,6 +98,7 @@
 # of Makefile.  These functions do the two bits of cleaning.
 clean_autotools(){
    rm -rf $libpng_autotools_files $libpng_libtool_files $libpng_autotools_dirs
+   rm -rf $libpng_autotools_extra
 }
 
 clean_configure(){