Add Init_priority support.

Add Init_priority support.

Added TARGET_ASM_CONSTRUCTOR and TARGET_ASM_DESTRUCTOR macros. These
macros allows users to control the order of initialization of objects
defined at namespace scope with the init_priority attribute by
specifying a relative priority.

ChangeLog:
2014-07-28  Ajit Agarwal  <ajitkum@xilinx.com>

	* config/microblaze/microblaze.c (microblaze_elf_asm_cdtor): New.
	(microblaze_elf_asm_constructor,microblaze_elf_asm_destructor): New.
	* config/microblaze/microblaze.h
	(TARGET_ASM_CONSTRUCTOR,TARGET_ASM_DESTRUCTOR): New Macros.

From-SVN: r214110