[dev.typeparams] all: merge dev.regabi (23b0c1f7) into dev.typeparams

Merge List:

+ 2021-02-02 23b0c1f7 [dev.regabi] all: merge master (fca94ab3) into dev.regabi
+ 2021-02-02 fca94ab3 spec: improve the example in Type assertions section
+ 2021-02-02 98f8454a cmd/link: don't decode type symbol in shared library in deadcode
+ 2021-02-02 1426a571 cmd/link: fix off-by-1 error in findShlibSection
+ 2021-02-01 32e789f4 test: fix incorrectly laid out instructions in issue11656.go
+ 2021-02-01 ca6999e2 [dev.regabi] test: add a test for inlining closures
+ 2021-02-01 0b6cfea6 doc/go1.16: document that on OpenBSD syscalls are now made through libc
+ 2021-02-01 26e29aa1 cmd/link: disable TestPIESize if CGO isn't enabled
+ 2021-02-01 6ac91e46 doc/go1.16: minor markup fixes
+ 2021-01-29 44361140 embed: update docs for proposal tweaks
+ 2021-01-29 68058edc runtime: document pointer write atomicity for memclrNoHeapPointers
+ 2021-01-28 c8bd8010 syscall: generate readlen/writelen for openbsd libc
+ 2021-01-28 41bb49b8 cmd/go: revert TestScript/build_trimpath to use ioutil.ReadFile
+ 2021-01-28 725a642c runtime: correct syscall10/syscall10X on openbsd/amd64
+ 2021-01-28 4b068caf doc/go1.16: document go/build/constraint package
+ 2021-01-28 376518d7 runtime,syscall: convert syscall on openbsd/arm64 to libc
+ 2021-01-27 aca22bdd [dev.regabi] cmd/compile: remove nested functions from expands_calls.go
+ 2021-01-27 667e08ba [dev.regabi] cmd/go: Use GOMAXPROCS to limit default build, compile parallelism
+ 2021-01-27 00f2ff5c api/go1.16: add go/build/constraint APIs
+ 2021-01-27 35334caf crypto/x509: remove leftover CertificateRequest field
+ 2021-01-27 a5a5e2c9 runtime: make sure to remove open-coded defer entries in all cases after a recover
+ 2021-01-27 8cfa0194 runtime: block console ctrlhandler when the signal is handled
+ 2021-01-27 ff9e8364 cmd/go: skip issue33139 when the 'cc' script command is unavailable
+ 2021-01-27 cd176b36 runtime: switch runtime to libc for openbsd/arm64
+ 2021-01-27 6c8fbfbd runtime: convert openbsd/arm64 locking to libc
+ 2021-01-27 5cdf0da1 syscall: clean up mkasm related changes
+ 2021-01-27 210f70e2 doc/go1.16: fix closing brace in .Export format
+ 2021-01-27 0f797f16 math: fix typo in sqrt.go code comment
+ 2021-01-26 9b636fea [dev.regabi] cmd/compile: missing last patch set for cl286013
+ 2021-01-26 f7dad5ea [dev.regabi] cmd/compile: remove leftover code form late call lowering work
+ 2021-01-26 8634a234 runtime,syscall: convert syscall on openbsd/amd64 to libc
+ 2021-01-26 1d5e1463 os: further document limitations around naked file descriptors
+ 2021-01-26 cf263e9f os: correct names in CreateTemp and MkdirTemp doc comments
+ 2021-01-26 ce8b3186 net/http/fcgi: remove locking added to prevent a test-only race

Change-Id: Ibd38d559c8a5b0aa32dd0d3a8cdf6876368a3aeb