Support compilation for Android platform. Reimplement -mandroid.

Support compilation for Android platform.  Reimplement -mandroid.

	* config.gcc (*linux*): Include linux-android.h and linux-android.opt.
	(*android*): Set ANDROID_DEFAULT.
	(arm*-*-linux*): Include linux-android.h.
	(arm*-*-eabi*): Don't include previous -mandroid implementation.
	* config/arm/eabi.h: Remove, move Android-specific parts ...
	* config/linux-android.h: ... here.  New file.
	* config/arm/eabi.opt: Rename to ...
	* config/linux-android.opt: ... this.
	(mandroid): Allow -mno-android option.  Initialize based on
	ANDROID_DEFAULT.
	* config/linux.h (STARTFILE_SPEC, ENDFILE_SPEC, CC1_SPEC, LIB_SPEC):
	Move logic to corresponding LINUX_TARGET_* macros.
	(TARGET_OS_CPP_BUILTINS): Define __ANDROID__, when appropriate.
	* config/linux-eabi.h (LINK_SPEC, CC1_SPEC, CC1PLUS_SPEC, LIB_SPEC,)
	(STARTFILE_SPEC, ENDFILE_SPEC): Define to choose between Linux and
	Android definitions.
	(LINUX_TARGET_OS_CPP_BUILTINS): Define __ANDROID__ if TARGET_ANDROID.
	* doc/invoke.texi (-mandroid, -tno-android-cc, -tno-android-ld):
	Document.

From-SVN: r159918