BUILD: Add build infrastructure for systemtap scripts
    
    Adds infrastructure that generatest the probes.h and probes.o from the
    dtrace probes.d file. The probes.d file is empty except for the provider
    name in this commit, its content will be added with later commits that
    actually add some content. The probes.d file is always distributed in
    the tarball so that distributions can optionally enable systemtap
    support.
    
    The generation is done using the "dtrace" command because the probes.d file
    is compatible with the Solaris dtrace format. Please see "man 1 dtrace"
    for more information on the dtrace format and the command line tool.
    
    In order to make libtool happy, a fake libtool object is generated. This
    hunk was taken from the libvirt code.
    
    The AM_V_GEN macro is used to make the build compatible with the silent
    build configuration.
    
    To enable systemtap probing, configure sssd with:
        --enable-systemtap
    In order to do so, the 'dtrace' command-line utility must be installed.
    On Fedora and RHEL, this package is installed as part of the
    "systemtap-sdt-devel" package.
    
    You'll also want the 'systemtap' package installed as well as the matching
    versions of kernel-devel and kernel-debuginfo on your machine.
    
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>