Update Doxygen configuration and comments

doc/doxygen/Doxyfile.in

lib/cmp_chunk.h

lib/common/cmp_entity.c

lib/common/cmp_support.h

lib/common/vsnprintf.c

lib/icu_compress/cmp_icu.c

lib/rdcu_compress/rmap.c

test/bench/leon3_grtimer.c

test/bench/leon3_grtimer_longcount.c

test/bench/leon_reg.h

test/fuzz/fuzz_compression.c

test/test_common/chunk_round_trip.c