Revert "Annotate fwd decls with the header containing the decl, not the top-most include."
Revert "Annotate fwd decls with the header containing the decl, not the top-most include."

This reverts commit 125a93e0e3562dac5d5a0429ce49a2b625025c26.
It fails in the following case (roottest/root/io/evolution/pragma_read):
dictionary for a/b.h which includes a/c.h as #include "c.h"
This will add a fwd decl with annotation "c.h", but this header cannot
be found. Instead we'd need "a/c.h"...

karies/cling,perovic/cling,karies/cling,karies/cling,root-mirror/cling,root-mirror/cling,marsupial/cling,marsupial/cling,root-mirror/cling,perovic/cling,perovic/cling,perovic/cling,marsupial/cling,karies/cling,marsupial/cling,root-mirror/cling,marsupial/cling,marsupial/cling,root-mirror/cling,karies/cling,perovic/cling,root-mirror/cling,karies/cling