Updated the generator to fully qualify std::string

The protobuf common.h header currently has a "using std::string;"
statement that pulls std::string into the google::protobuf namespace:
https://github.com/protocolbuffers/protobuf/blob/ce66f6047db44df3234bccd6fcf468bccc14a760/src/google/protobuf/stubs/common.h#L195

I plan to delete that line soon. To keep protobuf-c working, this commit
updates the generator to fully qualify std::string.

Travis CI: Test on other platforms

Travis CI now supports testing on arm64, ppc64le and s390x. It would
be nice to test on them.
Signed-off-by: Daniel Axtens <dja@axtens.net>

Bionic contains more recent compilers, which are required to have
the sanitisers work under s390x.

While we're at it, the 'sudo' key is deprecated, so remove it:

https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration

(It used to be used to mark VM vs docker container infrastructure,
but currently all amd64 builds run on VMs and all other archs run
inside LXD containers.)
Signed-off-by: Daniel Axtens <dja@axtens.net>

Pack nested messages inline

protoc-c: Remove leading underscores from structs

protobuf-c.c: Cast %lu args to unsigned long int

Standardize pkg-config for use by autotools and cmake, fix cmake tests

protobuf-c.h: Fix Windows DLL export (Fixes #331)

c_message.cc: Resolve name conflict (Fixes #389)

Signed-off-by: Markus Engel <engel@sero-systems.de>

Fixes #188.

Implements suggested fix from the issue:
The struct tag namespace is different from the type namespace. Use the
same symbol names (i.e. without leading underscores) in every namespace.

Also use BUILD_TESTS instead of CMAKE_BUILD_TYPE in other places in the
file.

Resolves an ambiguity that %zu was meant to address, since %zu is not
present on all platforms.

Fixes #357.

protobuf_c_empty_string is used in generated .pb-c.{c,h} files so it
should be exported properly.

lib.protobuf-c.io is no longer reachable.

-lpthread was missing from the linker command line. See
https://github.com/protocolbuffers/protobuf/issues/5107 for more
details.

.travis.yml: Run CMake debug build for verification

PACKAGE_DESCRIPTION is defined in configure.ac. PACKAGE_NAME,
PACKAGE_VERSION, and PACKAGE_URL come from AC_INIT.

This change will ensure that libprotobuf-c.pc.in could also be used by
CMake.

Bump version to 1.3.3

fix suport for MSVC static build

Signed-off-by: Markus Engel <engel@sero-systems.de>

protobuf-c.c: Make zigzag encoding more compact

Fixed some test assertions in test-generated-code2.c

.travis.yml: Reenable code coverage

Also match upstream code in src/google/protobuf/wire_format_lite.h

Makefile.am: Only enable the Issue #330 test case when building against protobuf 3.x

Issue #330 is a bug in proto3 behavior and the test case handling it
needs a 'syntax = "proto3";' line in its .proto file, which is not
supported by the protobuf 2 implementation.

Since we still support building against protobuf 2, this commit
conditionalizes the Issue #330 test case so that it is only built when
protobuf-c is being built against protobuf 3.

I fixed a couple test assertions here that seemed to be accidentally
using assignment (=) instead of equality (==).

Bump version to 1.3.2