Few DMM drivers already did it. This commit adjusts the remaining DMM
drivers, to set the "DC" flag for measurements in diode mode.
This fixes bug #144.
Although I don't have the hardware to test, the nature of the change and
the arrangement of driver code suggests it's good. When a meter already
communicated the "DC" status, the change does nothing and won't harm.
The change ensures "DC" is flagged for those meters which previously
didn't, which is desirable.
Since Autoconf places some important feature flags only into the
configuration header, it is necessary to include it globally to
guarantee a consistent build.
A few of these were pretty serious, like missing arguments,
passing integers where a string was expected, and so on.
In some places, change the types used by the code rather than
just the format strings.
Move the include flags for files in the source tree from
configure.ac to Makefile.am where they belong. Also use
AM_CPPFLAGS instead of CFLAGS/CXXFLAGS to make sure the
files in the build/source tree are always picked up first.
Also, remove the include/libsigrok sub-directory from the
search path, thereby making the <libsigrok/> prefix mandatory
when building libsigrok itself. This matches the convention
already imposed on users of the library.