Make base class for parser_state

Make base class for parser_state

This makes a new base class, expr_builder, for parser_state.  This
separates the state needed to construct an expression from the state
needed by the parsers.

gdb/ChangeLog
2019-04-04  Tom Tromey  <tom@tromey.com>

	* gdbarch.h, gdbarch.c: Rebuild.
	* gdbarch.sh (dtrace_parse_probe_argument): Change type.
	* stap-probe.h:
	(struct stap_parse_info): Replace "parser_state" with
	"expr_builder".
	* parser-defs.h (struct expr_builder): Rename from "parser_state".
	(parser_state): New class.
	* parse.c (expr_builder): Rename.
	(expr_builder::release): Rename.
	(write_exp_elt, write_exp_elt_opcode, write_exp_elt_sym)
	(write_exp_elt_msym, write_exp_elt_block, write_exp_elt_objfile)
	(write_exp_elt_longcst, write_exp_elt_floatcst)
	(write_exp_elt_type, write_exp_elt_intern, write_exp_string)
	(write_exp_string_vector, write_exp_bitstring)
	(write_exp_msymbol, mark_struct_expression)
	(write_dollar_variable)
	(insert_type_address_space, increase_expout_size): Replace
	"parser_state" with "expr_builder".
	* dtrace-probe.c: Replace "parser_state" with "expr_builder".
	* amd64-linux-tdep.c (amd64_dtrace_parse_probe_argument): Replace
	"parser_state" with "expr_builder".