Fix misstatement in comment in Makefile.shlib.

There is no need for "all: all-lib" to be placed before inclusion of
Makefile.shlib.  Makefile.global is what ensures that "all" is the
default target, and we already document that that has to be included
first.  Per comment from Pavel Raiskup.

Discussion: <1925924.izSMJEZO3x@unused-4-107.brq.redhat.com>

src/Makefile.shlib

@@ -47,9 +47,8 @@
 # clean-lib             delete the static and shared libraries from the build dir
 # maintainer-clean-lib  delete .def files built for win32
 #
-# Since `all-lib' is the first rule in this file you probably want to
-# have the `all' target before including this file. In the most simple
-# case it would look like this:
+# Typically you would add `all-lib' to the `all' target so that `make all'
+# builds the libraries.  In the most simple case it would look like this:
 #
 #     all: all-lib
 #