the functionality is already integrated into `zstd` through `--adapt` command

[dictBuilder] Fix deadlock in *COVER error case

Tweaks to create a single-file decompressor

The test script combines the sources then builds and runs an example. A futher example is built if the Emscripten compiler is available on the system. Documentation covers building.

The COVER and FASTCOVER dictionary builders can deadlock when
dictionary construction errors, likely because there are too few
samples, or too few distinct dmers. The deadlock only occurs when
there are errors.

Fixes #1746.

Work-in-progress. Added simple Emscripten WebGL example that adds 25kB when build with Zstd. Removed Buck (will replace). Minor correctness.

Combine script more robust and can output to a specified file. Initial buck files added (work in progress).

This reverts commit 0df29a4e, reversing
changes made to 69c875a0.

Add --size-hint=# option

[fuzz] Add a DEBUGLOG(3) statement to print file

The script will combine decompressor sources into a single file. The example shows this in use.

Enable it by building with this command:

```
./fuzz.py build all --debug 3
```

Add --stream-size=# option

[legacy] Fix buffer overflow in v0.2 and v0.4 raw literals decompression

[fuzz] Improve fuzzer build script and docs

The CHECK_F macros differ slightly (but eventually do the same thing). Older GCC needs to fallback on the old-style pragma optimisation flags.

clarifications on field `Block_Size`

remove extraneous doubled ;s

fixed very minor inefficiency (nbSeq==127)

Fix the build on GCC 4.x after 812e8f2a

Extends the fix in PR#1722 to v0.2 and v0.4. These aren't built into
zstd by default, and v0.5 onward are not affected.

I only add the `srcSize > BLOCKSIZE` check to v0.4 because the comments
say that it must hold, but the equivalent comment isn't present in v0.2.

Credit to OSS-Fuzz.

* Remove the `make libFuzzer` target since it is broken and obsoleted
  by `CC=clang CXX=clang++ ./fuzz.py build all --enable-fuzzer`. The
  new `-fsanitize=fuzzer` is much better because it works with MSAN
  by default.
* Improve the `./fuzz.py gen` command by making the input type explicit
  when creating a new target.
* Update the `README` for `--enable-fuzzer`.

Fixes #1727.