VS 2015 build issues

There are some issues with the build on VS 2015:
- On Win32 target (when Debug buid is selected) all functions that have 256 bit aligned parameters resut in build error, these can be fixed by adding the vectorcall calling convenion to these functions.
- Win32 VS compatible clz64 and ctz64 are missing (there is no BitScan_64 intrinsic for Win32 target). Can be fixed by using 2 32 bit BitScan_.
- Adding alignment to u64a/s64a causes issues on Win32 target when they are used as parameters. The alignment is not required, since these types are automatically aligned on the stack.
- Some VS warning parameters are broken
- __popcnt64 doesn't exist on Win32 target
- AlignedAllocator is missing constructors as required by c++ standard.

[patch.zip](https://github.com/01org/hyperscan/files/157658/patch.zip)