libgo: update to Go1.16rc1 release

[Ian Lance Taylor]

This patch updates libgo to the Go1.16rc1 release (the first 1.16
release candidate).  Bootstrapped and ran Go tests on
x86_64-pc-linux-gnu.  Committed to mainline.

The diffs are too large to attach, so I've trimmed out some
uninteresting changes to generated files.  They are of course
available in the repo.

Ian
-------------- next part --------------
A non-text attachment was scrubbed...
Name: patch.txt.bz2
Type: application/x-bzip
Size: 97828 bytes
Desc: not available
URL: <https://gcc.gnu.org/pipermail/gcc-patches/attachments/20210129/da606720/attachment-0001.bin>