Support the -D command line option for running benchmarks. The
benchmark code was slightly restructured to factor out the calls
that need to be different for each benchmark scenario. Since there
are now 4 scenarios (all combinations of fast/HC and with/without
dictionary), the logic was getting somewhat convoluted otherwise.
This was done by extending the compressionParameters struct that
previously contained just a single function pointer. It now
contains 4 function pointers for init/reset/compress/cleanup,
with the related state. The functions get a pointer to the
structure as their first argument (inspired by C++), so that they
can access the state values in the struct.
Improve formatting
Include static assert
Use UTIL_fseek to handle potential fseek limitation
Be explicit when refusing to read from stdin
Properly free dctx after use
Include valgrind tests
This behavior has been preserved for compatibility with existing ecosystem.
But it's problematic, as some environment start `lz4` without identifying stdout as console by default,
leading to a change of behavior for a same line of script.
A more sensible policy would be to default to stdout only when input is stdin.
Soft change for the time being : keep the behavior, just print a warning message.
User should prefer `-c` to explicitly select `stdout`.
Also : updated tests in Makefile to explicitly select `stdout` with `-c`.
This is the reverse of `-BD`, and the current default.
This command can be useful to reverse a previous `-BD` command.
It may in the future be more important
if `lz4` switches to generating dependent blocks by default.
instead of selected at compilation time depending on a macro.
This design makes it possible to have a single binary which supports both modes.
An advantageous side effect is that when doing `make; make install`
no additional binary is created during `make install`
(it used to create `lz4c`, because `make` would only build `lz4`)
