PR target/24837
	* config.gcc: Define UCLIBC_DEFAULT to 0 or 1.
	* opth-gen.awk: Handle Var and InverseMask together.
	* config/linux.opt (muclibc, mglibc): Use Var(linux_uclibc).
	* config/linux.h: Use #if not #ifdef for testing UCLIBC_DEFAULT.
	(TARGET_C99_FUNCTIONS): Test OPTION_GLIBC not TARGET_GLIBC.
	(CHOOSE_DYNAMIC_LINKER): Give an error for -mglibc and -muclibc
	used together.
	(UCLIBC_DYNAMIC_LINKER32, UCLIBC_DYNAMIC_LINKER64,
	LINUX_DYNAMIC_LINKER32, LINUX_DYNAMIC_LINKER64): Define.
	* config/alpha/linux-elf.h (GLIBC_DYNAMIC_LINKER,
	UCLIBC_DYNAMIC_LINKER, CHOOSE_DYNAMIC_LINKER,
	LINUX_DYNAMIC_LINKER): Define.
	(ELF_DYNAMIC_LINKER): Define to LINUX_DYNAMIC_LINKER.
	* config/alpha/linux.h (TARGET_C99_FUNCTIONS): Define to
	TARGET_GLIBC.
	* config/cris/linux.h (GLIBC_DYNAMIC_LINKER): Define.
	(CRIS_LINK_SUBTARGET_SPEC): Pass a -dynamic-linker option.
	* config/frv/linux.h (GLIBC_DYNAMIC_LINKER): Define.
	(LINK_SPEC): Use LINUX_DYNAMIC_LINKER.
	(TARGET_C99_FUNCTIONS): Don't define.
	* config/i386/linux.h (DYNAMIC_LINKER): Rename to
	GLIBC_DYNAMIC_LINKER.
	(SUBTARGET_EXTRA_SPECS): Use LINUX_DYNAMIC_LINKER.
	* config/i386/linux64.h (GLIBC_DYNAMIC_LINKER32,
	GLIBC_DYNAMIC_LINKER64): Define.
	(LINK_SPEC): Use LINUX_DYNAMIC_LINKER32 and
	LINUX_DYNAMIC_LINKER64.
	* config/ia64/linux.h (GLIBC_DYNAMIC_LINKER): Define.
	(LINK_SPEC): Use LINUX_DYNAMIC_LINKER.
	* config/m32r/linux.h (GLIBC_DYNAMIC_LINKE): Define.
	(LINK_SPEC): Use LINUX_DYNAMIC_LINKER.
	* config/m68k/linux.h (GLIBC_DYNAMIC_LINKER): Define.
	(LINK_SPEC): Use LINUX_DYNAMIC_LINKER.
	* config/mips/linux64.h (GLIBC_DYNAMIC_LINKER32,
	GLIBC_DYNAMIC_LINKER64, GLIBC_DYNAMIC_LINKERN32,
	UCLIBC_DYNAMIC_LINKERN32, LINUX_DYNAMIC_LINKERN32): Define.
	(LINK_SPEC): Use LINUX_DYNAMIC_LINKERN32, LINUX_DYNAMIC_LINKER64
	and LINUX_DYNAMIC_LINKER32.
	* config/mn10300/linux.h (GLIBC_DYNAMIC_LINKER): Define.
	(LINK_SPEC): Use LINUX_DYNAMIC_LINKER.
	* config/pa/pa-linux.h (GLIBC_DYNAMIC_LINKER): Define.
	(LINK_SPEC): Use LINUX_DYNAMIC_LINKER.
	* config/rs6000/linux.h (TARGET_C99_FUNCTIONS): Define to
	TARGET_GLIBC.
	* config/rs6000/linux64.h (TARGET_C99_FUNCTIONS): Likewise.
	(GLIBC_DYNAMIC_LINKER32, GLIBC_DYNAMIC_LINKER64,
	UCLIBC_DYNAMIC_LINKER32, UCLIBC_DYNAMIC_LINKER64,
	CHOOSE_DYNAMIC_LINKER, CHOOSE_DYNAMIC_LINKER,
	LINUX_DYNAMIC_LINKER32, LINUX_DYNAMIC_LINKER64): Define.
	(LINK_OS_LINUX_SPEC32): Use LINUX_DYNAMIC_LINKER32.
	(LINK_OS_LINUX_SPEC64): Use LINUX_DYNAMIC_LINKER64.
	* config/rs6000/sysv4.h (GLIBC_DYNAMIC_LINKER,
	UCLIBC_DYNAMIC_LINKER, CHOOSE_DYNAMIC_LINKER,
	LINUX_DYNAMIC_LINKER): Define.
	(LINK_OS_LINUX_SPEC): Use LINUX_DYNAMIC_LINKE.
	* config/s390/linux.h (GLIBC_DYNAMIC_LINKER32,
	GLIBC_DYNAMIC_LINKER64): Define.
	(LINK_SPEC): Use LINUX_DYNAMIC_LINKER32 and
	LINUX_DYNAMIC_LINKER64.
	* config/sh/linux.h (GLIBC_DYNAMIC_LINKER): Define.
	(SUBTARGET_LINK_SPEC): Use LINUX_DYNAMIC_LINKER.
	* config/sparc/linux.h (GLIBC_DYNAMIC_LINKER,
	UCLIBC_DYNAMIC_LINKER, CHOOSE_DYNAMIC_LINKER,
	LINUX_DYNAMIC_LINKER): Define.
	(LINK_SPEC): Use LINUX_DYNAMIC_LINKER.
	(TARGET_C99_FUNCTIONS): Define to TARGET_GLIBC.
	* config/sparc/linux64.h (GLIBC_DYNAMIC_LINKER32,
	GLIBC_DYNAMIC_LINKER64, UCLIBC_DYNAMIC_LINKER32,
	UCLIBC_DYNAMIC_LINKER64, CHOOSE_DYNAMIC_LINKER,
	LINUX_DYNAMIC_LINKER32, LINUX_DYNAMIC_LINKER64): Define.
	(LINK_ARCH32_SPEC): Use LINUX_DYNAMIC_LINKER32.
	(LINK_ARCH64_SPEC, LINK_SPEC): Use LINUX_DYNAMIC_LINKER64.
	(TARGET_C99_FUNCTIONS): Define to TARGET_GLIBC.
	* config/xtensa/linux.h (GLIBC_DYNAMIC_LINKER): Define.
	(LINK_SPEC): Use LINUX_DYNAMIC_LINKER.
	* doc/invoke.texi (-muclibc): Remove caveat about supported
	targets.

testsuite:
	* gcc.dg/glibc-uclibc-1.c, gcc.dg/glibc-uclibc-2.c: New tests.

From-SVN: r111235