ctf: fix the size of int and avoid duplicating it

ctf: fix the size of int and avoid duplicating it

An upcoming bitfield-capable release of libdtrace-ctf adds extra
consistency checking which identified embarrassing but heretofore
harmless bugs in dwarf2ctf's representation of basic types.

dwarf2ctf has to emit a few basic types "by hand", since these are used
in the representation of types one of CTF or DWARF does not bother to
encode more complex forms for (function pointers, always encoded as
'int (*)()' in CTF, and 'void').  Embarrassingly, we were getting the
size of 'int' wrong: it should be in bits but we were emitting a count
of bytes instead, leading to a CTF representation of a 4-bit int.
This is always overridden by an accurate representation built into
DTrace in real use, but libdtrace-ctf finds the inconsistency anyway.

Worse is that it emits a representation of 'int' twice, once by hand in
init_ctf_table() and then again when it comes across the real 'int' type
DIE in the debuginfo.  This is because we forgot to intern the types we
add by hand in the id_to_module and id_to_type hashes we use to detect
duplicate types, because we can only intern types we have a DWARF DIE
for, and these types either have no DIE at all or we just don't know
about it because we haven't even begun to traverse the debuginfo to look
up DIEs yet.

Fix this by adding a mark_shared_by_name() function which can be used to
intern basic types by name in these hashes.  It has hardwired knowledge
of the type ID notation, but no more such knowledge than is already
present in detect_duplicates_alias_fixup() and friends (no more than
that types with no associated filename or line number are preceded by
"////".)

Orabug: 25815129
Signed-off-by: Nick Alcock <nick.alcock@oracle.com>
Reviewed-by: tomas.jedlicka@oracle.com