AX_CODE_COVERAGE recently changed the way it embedded its Makefile rules in the output file: instead of using @CODE_COVERAGE_RULES@, users are now meant to include aminclude_static.am.
The new AX_CODE_COVERAGE is only in the latest autoconf-archive release, version 2019.01.06, which is inconveniently new, so bundle everything we need for the moment.
This requires us to stop using the deprecated CODE_COVERAGE_LDFLAGS (which we still used to support older versions of autoconf-archive) and replace them with CODE_COVERAGE_LIBS.
Consistently add CODE_COVERAGE_LIBS everywhere
We need to link the code coverage objects, directly or indirectly, into every executable and every shared library. The rule I've followed to make it clear that we do this, without too much repetition, is: each executable, shared library or convenience library has CODE_COVERAGE_LIBS in its LDADD or LIBADD, unless it is linked to a convenience library in the same directory that has CODE_COVERAGE_LIBS in its LIBADD.
Consistently add CODE_COVERAGE_CPPFLAGS everywhere
We forgot this in a couple of places.
First commit proposed for dbus-1.12. Second and third commits probably not.
Resolves #249 (closed)