Fix entry-values in C++ across CUs.
* dwarf2loc.c (call_site_to_target_addr) <FIELD_LOC_KIND_PHYSNAME>: Use
lookup_minimal_symbol. Add a comment.
* dwarf2read.c
(read_call_site_scope) <is_ref_attr> <die_is_declaration>: Prefer
DW_AT_linkage_name.
gdb/testsuite/
Fix entry-values in C++ across CUs.
* gdb.arch/amd64-tailcall-cxx.exp: New file.
* gdb.arch/amd64-tailcall-cxx1.S: New file.
* gdb.arch/amd64-tailcall-cxx1.cc: New file.
* gdb.arch/amd64-tailcall-cxx2.S: New file.
* gdb.arch/amd64-tailcall-cxx2.cc: New file.
