uterm: drm: move display_ops into vdrm object

Instead of passing display-ops to every helper store it in vdrm-objects.
During vdrm-setup we set the pointer and reuse it in all helpers. This
simplifies the function headers and allows calling them from
helper-callbacks without requiring a pointer from the respective user.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
genunifont: fix ftell() error checking

We need to use signed types to actually see errors from ftell(). Fix it by
using "long" for status bits now.

Reported-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
genunifont: fix MAX_DATA_SIZE to be in 8bit range

We only use uint8_t as length-counter so MAX_DATA_SIZE must be <256 to
make our length-checks work. This fixes a bug where we read invalid data
if someone uses modified genunifont data files. As this just produces
garbled glyphs if garbled data is given, this is actually not critical at
all.

Reported-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>