This reverts commit 8a03376544.
The patch needs to be split up and the gdbus/ changes were bogus
compared to the original commit message.
Conflicts:
Makefile.am
Makefile.obexd
profiles/cyclingspeed/cyclingspeed.c
profiles/heartrate/heartrate.c
src/error.c
Instead of trying to include config.h in each file over the tree and
possibly forgetting to include it, give a "-include config.h" argument
to the compiler so it's guaranteed that a) it will be included for all
source files and b) it will be the first header included.
gdbus/ directory is left out, since it would break other projects using
it.
Instead of defining _GNU_SOURCE in each source file (and potentially
forgetting in some), tell the build system we use extensions and let it
define _GNU_SOURCE in config.h.
