Libdwarf version 0.4.1

Two places where a carefully corrupted object file
could result in libdwarf crashing a caller due to
referencing memory outside the intended read area
have been fixed (DW202205-001 and DW202206-001).
One related to DW_FORM_ref_sig8, the other to
the .debug_pubnames section.

The library now accepts DW_AT_entry_pc in a CU DIE as a base address
when DW_AT_low_pc is missing (an extension used by
a current compiler).

Added function dwarf_suppress_debuglink_crc() to allow
callers to turn off doing a CRC calculation
reading GNU debuglink data (saves time for library
users accessing near-identical builds).