Restore original dll names, use Define constants.

Restore original dll names, use Define constants.

This changes set has no functional change, rather it cleans
up some aspects of a previous port.

When the hfa dlls were originally ported it was not known that
C# #defines could be used in the tests, so source files that
use #if were expanded to multiple source files with the preprocessing
being done manually. This changes goes back to using the original
files with appropriate define constants in the project files.

In addition, when these dlls were ported abbreviated names were
used. This change restores the dll names to the originals.

Commit migrated from https://github.com/dotnet/coreclr/commit/4d017e38094773f36b902f19031c834e22d97266