Here we should have been consuming both the thing we would be printing
and the indentation we would use on the next line, but in the case
where the printed thing was nil, we would only consume it, and not the
subsequent indentation. It worked out here, but the mistake could only
be made once, and only at the end.

Robert Brown's protobuf package falls back on the java_package option
as the lisp package name when there isn't a package declaration in the
schema. Emulate that behavior for better compatibility between code
generated by the packages.

Rather than hard-code assumptions about the size of a FIXNUM, check
the size of FIXNUM at compile time and generate code appropriate for
the number of bits we're working with, with FIXNUM optimizations
in place if appropriate.

Includes some changes from swmckay@gmail.com.

Conflicts:
	tests/qtest.lisp

Signed-off-by: Alejandro R Sedeño <asedeno@google.com>

Inspired by:
https://developers.google.com/protocol-buffers/docs/proto#extensions

Nested Extensions:

"A common pattern is to define extensions inside the scope of the
 extension's field type – for example, here's an extension to Foo of
 type Baz, where the extension is defined as part of Baz"

This fixes the unit test that broke in the previous commit

Conflicts:
	serialize.lisp

Reviewer: tunes