* config.gcc (LIBC_GLIBC, LIBC_UCLIBC, LIBC_BIONIC): Move constants
	to top level.
	* config/linux.h (LINUX_TARGET_OS_CPP_BUILTINS): Move Android-specific
	definitions ...
	* config/linux-android.h (ANDROID_TARGET_OS_CPP_BUILTINS): ... here.
	New macro.
	* config/arm/linux-eabi.h (TARGET_OS_CPP_BUILTINS): Use it.

From-SVN: r162315