Update X86 Bionic CRT files for unwind/exceptions

Several updates to Bionic crt*.o files to implement Linux/x86
stack unwind/exception handling.
Mark __dso_handle as hidden.
Note: Requires complete rebuild due to CRT changes. Google will
need to regenerate and check-in all the prebuilt x86 CRT object
files and libraries which link to them.

Change-Id: I191ce1afb0dee7bbc28dcd9694e5919226dbd070
Signed-off-by: Bruce J Beare <bruce.j.beare@intel.com>
Signed-off-by: Mark D Horn <mark.d.horn@intel.com>
Author: Lu, Hongjiu <hongjiu.lu@intel.com>
diff --git a/libc/arch-x86/bionic/crtend.S b/libc/arch-x86/bionic/crtend.S
index 884ba8b..68447e7 100644
--- a/libc/arch-x86/bionic/crtend.S
+++ b/libc/arch-x86/bionic/crtend.S
@@ -6,3 +6,10 @@
 
 	.section .fini_array, "aw"
 	.long 0
+
+	.section	.eh_frame,"a",@progbits
+	.align 4
+	.type	__FRAME_END__, @object
+	.size	__FRAME_END__, 4
+__FRAME_END__:
+	.zero	4