re PR target/49868 (Implement named address space to place/access data in flash memory)

libgcc/
	PR target/49868
	Extend __pgmx semantics to linearize memory.
	* config/avr/t-avr (LIB1ASMFUNCS): Add _xload_1, _movmemx.
	* config/avr/lib1funcs.S (__xload_1): New function.
	(__movmemx_qi, __movmemx_hi): New functions.
	(__xload_2, __xload_3, __xload_4): Rewrite to fit new __pgmx
	semantics.

gcc/
	PR target/49868
	Extend __pgmx semantics to linearize memory.
	* config/avr/avr.md (mov<mode>): Use avr_xload_libgcc_p to
	determine if code comes inline or from libgcc.
	(MOVMEM_r_d:HI): Add "w" to constraint for better preference.
	(movmem_qi, movmem_qi): Set constraint #2 to "n".
	(movmem_qi_elpm, movmem_hi_elpm): Remove insns.
	(movmemx_qi, movmemx_hi): New insns.
	(xload_<mode>_libgcc): Rewrite to new insn condition.
	(xload_<mode>): Remove insns.
	* config/avr/avr.c (avr_out_xload): Rewrite: Only need to handle
	cases that don't satisfy avr_xload_libgcc_p().
	(avr_addr_space_convert): Allow converting in any direction.
	(avr_addr_space_subset_p): Return always true.
	(avr_xload_libgcc_p): Rewrite to fit new __pgmx semantics.
	(avr_emit_movmemhi): Ditto.
	(avr_out_lpm): No need to handle ADDR_SPACE_PGMX any more.
	(avr_out_movmem): Ditto.
	(AVR_SYMBOL_FLAG_PROGMEM): New macro.
	(AVR_SYMBOL_SET_ADDR_SPACE): New macro.
	(AVR_SYMBOL_GET_ADDR_SPACE): New macro.
	(avr_encode_section_info): Encode 'progmem' in symbol flags.
	(output_reload_in_const): Don't zero-extend any 24-bit symbols.

From-SVN: r183058