This patch adds builtin support for some RTL builtins to avr backend.
One builtin implements loop for delay of specific number of ticks
(under the assumption IRQs are off), others simply map to machine
instructions like SEI, CLI, NOP, SLEEP, WDR, FMUL, FMAULS, FMULSU.

In addition, builtin macros are introduced so that use can easily
query if or if not a specific builtin is available. This might be
useful as builtin support evolves, because #ifdef is easier then to
twiddle out which version brings what builtin.

2011-04-06  Georg-Johann Lay  <avr@gjlay.de>

	* config/avr/avr.c: ("insn-codes.h", "optabs.h", "langhooks.h"):
	New Includes
	(avr_init_builtins, avr_expand_builtin,
	avr_expand_delay_cycles, avr_expand_unop_builtin,
	avr_expand_binop_builtin ): New functions.
	(avr_builtin_id): New enum
	(struct avr_builtin_description): New struct
	(bdesc_1arg, bdesc_2arg): New arrays describing some RTL builtins.
	(TARGET_INIT_BUILTINS, TARGET_EXPAND_BUILTIN): Define.
	* config/avr/avr.md (UNSPEC_FMUL, UNSPEC_FMULS, UNSPEC_FMULSU,
	UNSPECV_ENABLE_IRQS, UNSPECV_NOP, UNSPECV_SLEEP, UNSPECV_WDR,
	UNSPECV_DELAY_CYCLES): new enumeration values
	(UNSPEC_SEI, UNSPEC_CLI): Remove enumeration values
	("enable_interrupt"): Use UNSPECV_ENABLE_IRQS
	("disable_interrupt"): Use UNSPECV_ENABLE_IRQS
	("*rotlqi3_4"): rename insn to "rotlqi3_4"
	("delay_cycles_1", "delay_cycles_2", "delay_cycles_3",
	"delay_cycles_4", "nopv", "sleep", "wdr", "fmul", "fmuls",
	"fmulsu"): New insns
	* config/avr/avr-c.c: fix line endings
	(avr_cpu_cpp_builtins): New builtin defines: __BUILTIN_AVR_NOP,
	__BUILTIN_AVR_SEI, __BUILTIN_AVR_CLI, __BUILTIN_AVR_WDR,
	__BUILTIN_AVR_SLEEP, __BUILTIN_AVR_SWAP,
	__BUILTIN_AVR_DELAY_CYCLES, __BUILTIN_AVR_FMUL,
	__BUILTIN_AVR_FMULS, __BUILTIN_AVR_FMULSU.