ebtree is one piece using a lot of inlines and each tree root or node
definition needed by many of our structures requires to parse and
compile all these includes, which is large and painfully slow. Let's
move the very basic definitions to their own file and include it from
ebtree.h.
This is where other imported components are located. All files which
used to directly include ebtree were touched to update their include
path so that "import/" is now prefixed before the ebtree-related files.
The ebtree.h file was slightly adjusted to read compiler.h from the
common/ subdirectory (this is the only change).
A build issue was encountered when eb32sctree.h is loaded before
eb32tree.h because only the former checks for the latter before
defining type u32. This was addressed by adding the reverse ifdef
in eb32tree.h.
No further cleanup was done yet in order to keep changes minimal.