Add support for Bionic C library
	gcc/
	* config.gcc (LIBC_GLIBC, LIBC_BIONIC, LIBC_UCLIBC): New tm_define
	macro.
	(DEFAULT_LIBC): New tm_define macro set to one of LIBC_*.
	(bfin*-uclinux, moxie-*-uclinux*, m68k-*-uclinux*): Update.

	* config/linux.h (OPTION_GLIBC, OPTION_UCLIBC, OPTION_BIONIC): Define.
	(LINUX_TARGET_OS_CPP_BUILTINS): Define __gnu_linux__ only for GLIBC.
	(CHOOSE_DYNAMIC_LINKER1, CHOOSE_DYNAMIC_LINKER): Make it easier
	to support multiple C libraries.  Handle Bionic.
	(BIONIC_DYNAMIC_LINKER, BIONIC_DYNAMIC_LINKER32,)
	(BIONIC_DYNAMIC_LINKER64): Define.
	(LINUX_DYNAMIC_LINKER, LINUX_DYNAMIC_LINKER32, LINUX_DYNAMIC_LINKER64):
	Update.
	(TARGET_HAS_SINCOS): Enable for Bionic.

	* config/linux.opt: Rewrite to handle more than 2 C libraries.  Make
	the last option specified on command line take effect.
	(linux_uclibc): Rename to linux_libc, initialize using DEFAULT_LIBC.
	(mbionic): New.
	(mglibc, muclibc): Update.

	* config/alpha/linux-elf.h, config/rs6000/linux64.h,
	* config/rs6000/sysv4.h (CHOOSE_DYNAMIC_LINKER): Update to use
	DEFAULT_LIBC.

	* doc/invoke.texi (-mglibc, -muclibc): Update.
	(-mbionic): Document.

	gcc/testsuite/
	* gcc.dg/glibc-uclibc-1.c, gcc.dg/glibc-uclibc-2.c: Remove, no longer
	necessary.

From-SVN: r159917