Same code of the proto2 test but with the corresponding proto3 file

This is a first cut at adding proto3 support.

As far as I understand protobuf-c already has pretty much everything
needed once it is built using a new version of protobuf itself.
The only missing thing is that in proto3 all fields are optional and
having to manually set has_foo is inconvenient.

This patch special cases the proto3 syntax files so that structs for the
bytes, enum and primitive fields do not emit the has_ field.

It also adds PROTOBUF_C_LABEL_NONE to the label enum that is used for
proto3 fields. When a fields has this label, the quantifier is not
consulted and instead the field is packed/unpacked depending on
whether it has a value different from NULL/0.

Make init_value const

rm argument fix for solaris

Relax autoconf constraint from v2.64 -> v2.63 (so that it works on SL6)

protobuf-c: fix: make dist

fixed cmake build if built as  part of an external project

remove .pb.{cc,h} in distdir instead of top_distdir in order to
prevent removing files from other projects when protobuf-c is
included as an autotools subproject.
Signed-off-by: Gregory Detal <gregory.detal@tessares.net>

protoc-c/c_message.cc: Force int size on oneof enums

http://lists.llvm.org/pipermail/llvm-foundation/2016-May/000020.html

travis-ci/travis-ci#6120

Fixes #220. Patch by Dave Benson from the mailing list thread.

Fix bigendian -Wunused-label warning

Fix ISO C90 -Wdeclaration-after-statement warnings

Fix -Wsign-compare warnings in int32_size()

From https://developers.google.com/protocol-buffers/docs/proto#optional:
If the default value is not specified for an optional element, a
type-specific default value is used instead: for strings, the default
value is the empty string. For bools, the default value is false. For
numeric types, the default value is zero. For enums, the default value
is the first value listed in the enum's type definition. This means care
must be taken when adding a value to the beginning of an enum value
list.

Prior to this change, protoc-c set the default enum value to 0, whether
or not 0 was the first value listed in the enum's type definition (or if
it even was listed at all).

Using the old "protoc-c" command directly is still supported
through a symlink.

Using {} as an initializer fails on MSVC
Signed-off-by: Paolo Borelli <pborelli@gnome.org>

I've moved the guide to its own domain some time ago, fix the reference to avoid the redirects.

Remove a redundant test and add two large number test cases.

This change helps keep protobuf-c compatible with systems where int is
less than 4 bytes long. This change also makes left shifts more
consistent.