autotools: remove requirement on md5sum, which is not used anymore

configure.in

@@ -31,11 +31,6 @@ else
    export AWK
 fi
 
-AC_PATH_PROGS(MD5SUM, md5sum, "no")
-if test x$MD5SUM = "xno"; then
-    AC_MSG_ERROR([md5sum is required])
-fi
-
 AC_PATH_PROGS(MKTEMP, mktemp, "no")
 if test x$MKTEMPT = "xno"; then
     AC_MSG_ERROR([mktemp is required])

lib/Makefile.am

@@ -9,7 +9,6 @@ edit = sed \
     -e "s,@BASH\@,$(BASH),g" \
     -e "s,@AWK\@,$(AWK),g" \
     -e "s,@SED\@,$(SED),g" \
-    -e "s,@MD5SUM\@,$(MD5SUM),g" \
     -e "s,@MKTEMP\@,$(MKTEMP),g" \
     -e "s,@libdir\@,$(pkglibdir),g"