* exception.h (class exception): Add handler_installed member.
	Change parameters to handle method to match high-level exception
	handler calls.
	(exception::exception): On x86_64, install exception handler only
	once.  Explain what we do.
	* exceptions.cc (_AFMT): Change to only 11 digits on x86_64.
	(cygwin_exception::dump_exception): Print Rip with only 11 digits.
	Print 64 bit registers with 0-padding.
	(class stack_info): Add members c and hist on x86_64.
	(stack_info::init): Take PCONTEXT rather than bool as third parameter.
	Tweak code accordingly.  Initialize c and hist on x86_64.
	(stack_info::walk): Add implementation for x86_64.  Drop unneeded
	#ifndef in 32 bit code.
	(cygwin_exception::dumpstack): Call thestack.init with context as
	parameter.  Change header output for x86_64.
	(cygwin_stackdump): Prefer RtlCaptureContext over GetThreadContext.
	(CYG_EXC_CONTINUE_EXECUTION): Define generic definition matching all
	platforms.
	(CYG_EXC_CONTINUE_SEARCH): Ditto.
	(exception::handler_installed): Define here.
	(exception::handle): Define according to declaration in exception.h.
	Create 32 bit parameters as local variable on 64 bit.  Change all
	return statements to use generic definitions.  Simplify setting framep
	on x86_64.  Disable setting frame-based exception handler on x86_64.
	Fix formatting of klog output for x86_64.
	(signal_exit): Create context for cygwin_exception creation.
	(sigpacket::process): Prefer RtlCaptureContext over GetThreadContext.
	* wincap.h (wincaps::has_rtl_capture_context): New element.
	* wincap.cc: Implement above element throughout.
	* cygwin64.din: Remove all deprecated cygwin32_foo and cygwin_foo
	path conversion functions.
	* path.cc: Disable aforementioned functions on x86_64.
	* include/sys/cygwin.h: Don't declare aforementioned functions on
	x86_64.