Update: Adapt to C standard GNU89 with GCC extensions

examples/example_cmp_icu.c

examples/example_cmp_rdcu.c

lib/common/byteorder.h

lib/common/cmp_data_types.c

lib/common/cmp_entity.c

lib/decompress/cmp_max_used_bits_list.c

lib/decompress/decmp.c

lib/icu_compress/cmp_icu.c

lib/rdcu_compress/cmp_rdcu.c

lib/rdcu_compress/rmap.c

meson.build

programs/cmp_io.c

programs/cmp_tool.c