In some place compiler extensible headers force fixed source layout

[dnakamura]

In some places the extensible headers mechanism used by the compiler component is flawed. It requires that a consuming project have a fixed relation between their source code and the omr source code, which may not be desired by the consuming project. In order to remedy this, the extensible headers with a name of <Foo>.hpp should be named OMR<Foo>.hpp so that the consumer provided extended header can include the base header simply instead of having to specify a path to the omr directory (eg (#include "omr/compiler/Foo.hpp")

Note: This is already the convention used by the majority of the extensible header files