Based on a patch from Daniel Berlin (dberlin@dberlin.org).
* symtab.h: Add opaque declarations of struct axs_value and
struct agent_expr.
(enum address_class): Add LOC_COMPUTED and LOC_COMPUTED_ARG.
(struct location_funcs): New type.
(struct symbol): Add "loc" to aux_value.
(SYMBOL_LOCATION_BATON, SYMBOL_LOCATION_FUNCS): New macros.
* dwarf2read.c: Include "dwarf2expr.h".
(dwarf2_symbol_mark_computed): New function.
(read_func_scope): Use it.
(var_decode_location): New function.
(new_symbol): Use it.
* dwarf2expr.c, dwarf2expr.h, dwarf2loc.c, dwarf2loc.h: New files.