A question on the stack alignment on 64 bit arch

[Xiaobin Lu]

Hi folks,

While I am fixing the stack alignment bug (6792301), I noticed that on 
64 bit implementation of generate_native_wrapper, currently we actually 
align the stack frame with 32 bytes (line 1289 & 1290 in 
sharedRuntime_x86_64.cpp). If we want to consider StackAlignmentInBytes, 
we probably want to align the frame with 16 bytes. Will this have any 
bad effects? I have run a few tests with 16 bytes aligned stack frame 
and it seemed running fine.

Thanks,
-Xiaobin