Pull in changes from HEAD
* child_info.h (spawn_info): Define asm symbol without leading
	underscore for x86_64.
	(fork_info): Ditto.
	* cygwin.sc.in (__CONCAT1): Define.
	(__CONCAT): Define.
	(_SYM): Define.
	(_data_start__): Define using _SYM macro to accommodate multiple
	platforms.
	(_data_end__): Ditto.
	(_bss_start__): Ditto.
	(_bss_end__): Ditto.
	(_cygheap_start): Ditto.
	(_cygheap_end): Ditto.