Draft: Move dependencies to separate files.
For all makefiles run by amu_machine, move the dynamic dependencies
to a separate file, Makefile/d. stripdepnd is aliased to delete
this on clean.
- Git tools, such as git gui will not show the Makefiles as modified and offer to commit the changes.
- It will be possible checkout different versions without cleaning the source tree and recompiling from scratch.
- It will be possible to build RISC OS with a security policy that does not allow modification of source files.
This supersedes RiscOS/Utilities/Release/srcbuild!1 (closed) and !3 (closed).
The hazard of losing dynamic dependences on checking out an older version can be partially protected against by merging RiscOS/Sources/Internat/Messages!1 immediately prior which will cause git to raise if earlier versions are checked out without cleaning.