* All copyright lines now have -2020 instead of -present
* All copyright lines include "Facebook, Inc"
* All licenses are now standardized

The copyright in `threading.{h,c}` is not changed because it comes from
zstdmt.

The copyright and license of `divsufsort.{h,c}` is not changed.

Align decompress sequences loop to 32+16 bytes

The alignment is added before the loop, so this shouldn't hurt
performance in any case. The only way it hurts is if there is already
performance instability, and we force it to be stable but in the bad
case.

This consistently gets us into the good case with gcc-{7,8,9} on an
Intel i9-9900K and clang-9. gcc-5 is 5% worse than its best case but has
stable performance. We get consistently good behavior on my Macbook Pro
compiled with both clang and gcc-8. It ends up in the 50% from DSB and
50% from MITE case, but the performance is the same as the 85% DSB case,
so thats fine.

[opt] Update repcodes less often

[contrib] Edit distance match finder

[doc] targetLen -> targetLength

[opt] Small icc level 1 compression speed gain using #pragma vector 

_BitScan{Reverse,Forward} add check for undefined

Adding --[no-]content-size to the cli

Removing no-tree-vectorize for intel

[opt] Don't recompute initial literals price

[ci] Adding icc make check to travis

Add issue templates to zstd

LZ4 just added this. I think it would be helpful here too.

[doc] Fixing ZSTD_c_compressionLevel confusing note

[zstdgrep] Log zstd decompression errors to stderr