Replace panics with error returns

so that malformed input doesn't make protodump panic

Account for (void) argument lists

Handle DW_AT_class_type

the same way as DW_AT_structure_type

Handle enumerations that don't have DW_AT_encoding

e.g. rust's std::cmp::Ordering

... and fetch the encoding from the underlying type, if it's a base
type.

Handling underlying types that are not base type is TODO (?), yet to be
found in the wild.

Add doc comments

Better type handling

- Parse types into proper structs
- Parse type definitions
- Handle anonymous functions
- Handle subroutine parameters

Make prototypes names bold

Instead of making the types bold, make the prototype names bold.
This makes it easier to tell the names apart.

Don't show type aliases

Properly iterate through debug entries

1/ Filter entries that have the DW_AT_declaration attribute set to true
   (this attribute means they are incomplete, e.g. parameter names are
   missing),
2/ Use next_dfs+next_sibling instead of next_entry, mostly for a
   clarity.

Allow parameters to have no name

diff mode: don't print any error message

man page: add an entry for the diff mode

diff mode

cargo update

Merge goblin and object usage

since both do the same thing

Fix typos

Update README.md and add a man page

Do not group by files by default

cargo clippy

Add options to show local, global and imported symbols