After commit 0c9d8e59 ("Fix undefined behavior by casting to uint64_t
before left shift"), the -Wno-shift-count-overflow flag is no longer
necessary to suppress compilation warnings. This commit removes the
flag, allowing the compiler to provide appropriate warnings for any
potential future cases of shifting too many bits.
Additionally, after commit eaf4a299 ("make redqueen hashmap not
default"), the hashmap is no longer in use. Therefore, this commit also
removes the hashmap from the GNUmakefile.
* Always compile with -ldl when building for CODE_COVERAGE
When building with CODE_COVERAGE, the afl runtime contains code that
calls `dladdr` which requires -ldl. Under most circumstances, clang
already adds this (e.g. when building with pc-table), but there are some
circumstances where it isn't added automatically.
* Add visibility declaration to __afl_connected
When building with hidden visibility, the use of __AFL_LOOP inside such
code can cause linker errors due to __afl_connected being declared
"hidden".
* Update docs to clarify that CODE_COVERAGE=1 is required for dynamic_covfilter
Currently, if I build like with Clang, I'll get:
```bash
make LLVM_CONFIG=llvm-config-15 CC=clang-15 CXX=clang++-15
<snip>
[+] Everything seems to be working, ready to compile. (gcc version 12.1.0 (Ubuntu 12.1.0-2ubuntu1~22.04) )
clang-15 -O2 -D_FORTIFY_SOURCE=1 ....
```
Which is somewhat confusing. Fix this, and in a way that still outputs
the correct version info for Clang and GCC. Use `--version`, and pick
the first line, as that is where they are consistent in output. `clang
-v` gives the version first, whereas `gcc -v` gives the version on the
last line.
We switch to using $(CC), otherwise we also get incorrect output,
and dropping CCVER altogether, given this is it's only use.
