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.
Add LIBUSB_CALL where needed to avoid warnings such as the following:
In file included from src/hardware/hantek-dso/api.c:34:0:
src/hardware/hantek-dso/dso.h:212:13:
note: expected 'libusb_transfer_cb_fn' but argument is of type 'void (*)(struct libusb_transfer *)'
SR_PRIV int dso_get_channeldata(const struct sr_dev_inst *sdi,
^