Rework sparc PIC macros so crt{i,n}.S can use them too.

Rework sparc PIC macros so crt{i,n}.S can use them too.

	* sysdeps/unix/sparc/sysdep.h (SPARC_PIC_THUNK): New macro.
	(SETUP_PIC_REG): Use SPARC_PIC_THUNK and don't save and restore
	%o7 across the call.
	(SETUP_PIC_REG_LEAF): Do %o7 save/restore in this new macro
	instead.
	* sysdeps/unix/sysv/linux/sparc/sparc32/sysdep.h: Use
	SETUP_PIC_REG_LEAF.
	* sysdeps/unix/sysv/linux/sparc/sparc64/sysdep.h: Likewise.
	* sysdeps/sparc/crti.S: Use SETUP_PIC_REG.
	* sysdeps/sparc/crtn.S: Likewise.