PR15688: Set pragma:vma when dwflpp uses _stp_umodule_relocate
* dwflpp.cxx (dwflpp::emit_address): Use pragma:vma when needed, rather
than trying to enable_task_finder. This also leaves the opportunity
for this generated code to be optimized out, such that vma-tracking
may not be needed after all.
* elaborate.cxx (embeddedcode_info::visit_embeddedcode): Before enabling
the vma-tracker, check if runtime=dyninst for PR15052. This turns an
ugly pass-4 failure into a nicer pass-2 message.
* session.cxx (systemtap_session::parse_cmdline): Don't force vma here
for userspace -d modules; dwflpp will add pragma:vma as needed.
* tapsets.cxx (dwarf_atvar_expanding_visitor::visit_atvar_op): Don't
enable_vma_tracker manually; dwflpp will add pragma:vma as needed.
* testsuite/systemtap.base/sdt_global_var.exp: Clear this setup_kfail.