[foreign-abi] RFR: 8228762: import CallingSequenceBuilder unit tests

[Nick Gasson]

Hi,

Bug: https://bugs.openjdk.java.net/browse/JDK-8228762
Webrev: http://cr.openjdk.java.net/~ngasson/foreign/8228762/

This patch modifies the three CallingSequenceTest unit tests from the 
foreign branch to work with the MemoryLayout API in foreign-abi. Also 
changed the AArch64 test to use CallingSequenceTestBase to match 
Windows/SysV.

I also modified MemoryLayouts so the AArch64 C_* constants are all 
little rather than big endian. Although the ABI officially supports both 
big and little endian, big endian is almost never used in practice, and 
in Hotspot we only support little endian AArch64.

Thanks,
Nick