Build failure with recent lld

[aaronmondal]

Upstream lld flipped --undefined-version(https://reviews.llvm.org/D135402). This causes recent Clang toolchains to break:

Default config:

ld.lld: error: version script assignment of 'ZLIB_NG_2.0.0' to symbol 'zng_adler32_c' failed: symbol not defined
ld.lld: error: version script assignment of 'ZLIB_NG_2.0.0' to symbol 'zng_zlibng_string' failed: symbol not defined
ld.lld: error: version script assignment of 'ZLIB_NG_2.0.0' to symbol 'zng_version' failed: symbol not defined
ld.lld: error: version script assignment of 'local' to symbol 'zng_inflate_fast' failed: symbol not defined
ld.lld: error: version script assignment of 'local' to symbol 'zng_zcalloc' failed: symbol not defined
ld.lld: error: version script assignment of 'local' to symbol 'zng_zcfree' failed: symbol not defined
ld.lld: error: version script assignment of 'local' to symbol 'zng_gz_error' failed: symbol not defined
ld.lld: error: version script assignment of 'ZLIB_NG_GZ_2.0.0' to symbol 'zng_gzoffset64' failed: symbol not defined
ld.lld: error: version script assignment of 'ZLIB_NG_GZ_2.0.0' to symbol 'zng_gzopen64' failed: symbol not defined
ld.lld: error: version script assignment of 'ZLIB_NG_GZ_2.0.0' to symbol 'zng_gzseek64' failed: symbol not defined
ld.lld: error: version script assignment of 'ZLIB_NG_GZ_2.0.0' to symbol 'zng_gztell64' failed: symbol not defined

ZLIB_COMPAT config:

ld.lld: error: version script assignment of 'local' to symbol 'inflate_fast' failed: symbol not defined
ld.lld: error: version script assignment of 'local' to symbol 'inflate_table' failed: symbol not defined
ld.lld: error: version script assignment of 'local' to symbol 'zcalloc' failed: symbol not defined
ld.lld: error: version script assignment of 'local' to symbol 'zcfree' failed: symbol not defined

[mtl1979]

At least zng_adler32_c should not be exported anymore...
zng_zlibng_string should be zlibng_string and zng_version should be zlibng_version.
zng_inflate_fast and inflate_fast might need workaround as those are in functable now.
inflate_table doesn't exist at all, but zng_inflate_table is internal symbol.
zng_zcalloc should be zng_calloc and zng_zcfree should be zng_cfree.
zng_gz_error should be just gz_error.
zng_gzoffset64, zng_gzopen64, zng_gzseek64 and zng_gztell64 do not exist, functions with 64 suffix only exist in compatibility mode.

@Dead2 @nmoinvaz

[Dead2]

#1421 passes for both normal and compat on my local x86-64 machine.
I did not test any other arches for bugs, but hopefully there are none.

It obviously also fails with WITH_GZFILEOP=OFF, and we'd need a separate set of map files without those (or .in files that we add depending on the need). I am not planning to tackle this one myself at the moment.

Edit: Wrong PR number

[aaronmondal]

I'm amazed at the swiftness with which this was handled. Thanks a lot!