libpam: fix package source to unbreak BB build

Yesterday's CVE-fix changed the package source URL to an invalid location.
Reverting this change to unbreak builds.

Signed-off-by: Steven Barth <steven@midlink.org>

libs/libpam/Makefile

@@ -12,7 +12,7 @@ PKG_VERSION:=1.1.8
 PKG_RELEASE:=4
 
 PKG_SOURCE:=Linux-PAM-$(PKG_VERSION).tar.bz2
-PKG_SOURCE_URL:=http://www.linux-pam.org/
+PKG_SOURCE_URL:=http://www.linux-pam.org/library/
 PKG_MD5SUM:=35b6091af95981b1b2cd60d813b5e4ee
 PKG_INSTALL:=1
 PKG_FIXUP:=autoreconf