RFR (M): 8188813: Generalize OrderAccess to use templates

[Erik Österlund]

Hi,

Now that Atomic has been generalized with templates, the same should to 
be done to OrderAccess.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8188813

Webrev:
http://cr.openjdk.java.net/~eosterlund/8188813/webrev.00/

Testing: mach5 hs-tier3

Since Atomic already has a mechanism for type checking generic arguments 
for Atomic::load/store, and OrderAccess also is a bunch of semantically 
decorated loads and stores, I decided to reuse the template wheel that 
was already invented (Atomic::LoadImpl and Atomic::StoreImpl).
Therefore, I made OrderAccess privately inherit Atomic so that this 
infrastructure could be reused. A whole bunch of code has been nuked 
with this generalization.

It is worth noting that I have added PrimitiveConversion functionality 
for doubles and floats which translates to using the union trick for 
casting double to and from int64_t and float to and from int32_t when 
passing down doubles and ints to the API. I need the former two, because 
Java supports volatile double and volatile float, and therefore runtime 
support for that needs to be able to use floats and doubles. I also 
added PrimitiveConversion functionality for the subclasses of oop 
(instanceOop and friends). The base class oop already supported this, so 
it seemed natural that the subclasses should support it too.

Thanks,
/Erik