configure.ac: fix golang binary check

When checking the version of golang, test the major part of the string
(1.XX.yy), and fix up the error message to not mislead the minimum
version.

Fixes #202

configure.ac

@@ -83,17 +83,17 @@ if test ! x"$with_golang" = xno; then
 	if test -n "$GO" ; then
 	    GOVERSIONOPTION=version
 	    go_version=$($GO $GOVERSIONOPTION | sed -e 's/go version //')
-	    AC_MSG_CHECKING([whether go version is >= 1.4.x])
+	    AC_MSG_CHECKING([whether go version is >= 1.14.x])
 	    case $go_version in
-	    go1.[14]*)
+	    go1.1[456789]*)
 	      AC_MSG_RESULT([yes - version is: $go_version])
 	      with_golang="yes"
 	      GO=
 	      ;;
 	    *)
 	      AC_MSG_RESULT([no - version is: $go_version])
 	      with_golang="no"
-	      problem_golang=": version of go ($go_version) <= 1.4.x"
+	      problem_golang=": version of go ($go_version) <= 1.14.x"
 	      ;;
 	    esac
 	fi