ffprobe: fix consistency checks in parse_read_intervals()

Move array size assert after the count increment, and avoid strchr() NULL
dereference on p.

Should fix FFmpeg coverity issue #1108581.
Support FF_DISABLE_DEPRECATION_WARNINGS with icc on Linux.
fate: enable hevc tests

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>