Add .cfi_startproc and endproc markers

Helps a bit... Now, if I revert the hackish arm64 change to ucbhelper,
instead of "terminating with uncaught exception" I get "terminating
with unexpected exception";) But, at least with the stack correctly
unwound to BaseContent::execute(), I think. Actually of course I don't
really understand much of this.

Change-Id: Iacb4342414cb84f9db31f9a40c7a136cc5d191a6

bridges/source/cpp_uno/gcc3_ios_arm/helper.s

@@ -49,6 +49,7 @@ _privateSnippetExecutor:
 
 _privateSnippetExecutor:
 
+    .cfi_startproc
     // _privateSnippetExecutor is jumped to from each of the
     // codeSnippet_*  generated by generate-snippets.pl
 
@@ -76,6 +77,7 @@ _privateSnippetExecutor:
     ldp     x8, lr, [sp, #0]
     add     sp, sp, #144
     ret     lr
+    .cfi_endproc
 
 #else
     // i386 code, for the simulator