fstrm: convert FSTRM_CONTROL_* to enums
fstrm: add fstrm_control interface
t/test_control: new
fstrm_dump: rewrite to use new fstrm_control interface for decoding control frames
t/test_fstrm_io_unix: use designated initializer instead of memset()
t/test_fstrm_io_file: read_input(): fix fread() checks
t/test_fstrm_io_unix: read_inpu(): fix fread() checks
fstrm: move macros and enums into more relevant sections
rename FSTRM_RES_* to fstrm_res_*