Factor our the common parts of the invocation infos for C and Perl code
Do not try to free the "free after call" list twice
Handle arg and type infos in the common invocation code

Also, rename a struct field to avoid confusion.
Fix a leak when throwing an exception during C invocation
Fix a marshalling bug with Perl code and array args

When invoking Perl code with array args, use the correct type for the length
arg.  Previously, we used the type of the array arg to convert the length arg
to a Perl value.  That is, in the most common case, we treated an integer as a
pointer.  This works OK on little-endian systems, but most likely breaks on
big-endian ones.
Fix an endian-ness bug with the array length marshalling

We were always accessing array length args as gsize, but on big-endian systems
this does not work when the actual type of the arg is bigger than gsize.  This
occurred on ppc64.

https://rt.cpan.org/Ticket/Display.html?id=98463
Correctly detect too few args given to constructors

When calling a C constructor that does not expect any arguments, the Perl
wrapper expects only the class name as an argument, following the usual
"Package->new" convention.  Incorrectly using "Package::new" instead previously
resulted in a confusing error message due to an unsigned integer overflow.
Fix a few integer conversion issues

Most of these changes just hush compiler warnings, but some also assert
formerly implicit assumptions.
Properly convert Perl callback return values on big-endian systems

ffi expects certain return value semantics that we were not satisfying.  This
lead to incorrect conversions on big-endian systems.

https://rt.cpan.org/Ticket/Display.html?id=98463
Use the correct storage type for converting enums and flags

Previously, we always simply interpreted enum and flags values as being of type
"long".  Depending on the permissible values and on the platform, the actual
type used by the compiler might differ from that, however.  This caused no
immediate problems on little-endian systems, but led to issues on big-endian
systems.

https://rt.cpan.org/Ticket/Display.html?id=98463
Mention the recent ppc64 fixes in NEWS