Implement 64-bit double functions.

Implement 64-bit double functions.

gcc/
	PR target/92055
	* config.gcc (tm_defines) [target=avr]: Support --with-libf7,
	--with-double-comparison.
	* doc/install.texi: Document them.
	* config/avr/avr-c.c (avr_cpu_cpp_builtins)
	<WITH_LIBF7_LIBGCC, WITH_LIBF7_MATH, WITH_LIBF7_MATH_SYMBOLS>
	<WITH_DOUBLE_COMPARISON>: New built-in defines.
	* doc/invoke.texi (AVR Built-in Macros): Document them.
	* config/avr/avr-protos.h (avr_float_lib_compare_returns_bool): New.
	* config/avr/avr.c (avr_float_lib_compare_returns_bool): New function.
	* config/avr/avr.h (FLOAT_LIB_COMPARE_RETURNS_BOOL): New macro.
libgcc/
	PR target/92055
	* config.host (tmake_file) [target=avr]: Add t-libf7,
	t-libf7-math, t-libf7-math-symbols as specified by --with-libf7=.
	* config/avr/t-avrlibc: Don't copy libgcc.a if there are modules
	depending on sizeof (double) or sizeof (long double).
	* config/avr/libf7: New folder.
libgcc/config/avr/libf7/
	PR target/92055
	* t-libf7: New file.
	* t-libf7-math: New file.
	* t-libf7-math-symbols: New file.
	* libf7-common.mk: New file.
	* libf7-asm-object.mk: New file.
	* libf7-c-object.mk: New file.
	* asm-defs.h: New file.
	* libf7.h: New file.
	* libf7.c: New file.
	* libf7-asm.sx: New file.
	* libf7-array.def: New file.
	* libf7-const.def: New file.
	* libf7-constdef.h: New file.
	* f7renames.sh: New script.
	* f7wraps.sh: New script.
	* f7-renames.h: New generated file.
	* f7-wraps.h: New generated file.

From-SVN: r279994