Revert "Delete version.h on make clean"

This reverts commit fdb67b69f9e9f06de278711ef8fbeeed34988046.
Revert "Make version a prerequisite for version.h instead of all."

This reverts commit 697d818a9939cfbf4d9e52f970ea8af9d2973574.
make clean deletes version.h, if it exists