[release-branch.go1.8] all: final merge of master into Go 1.8 release branch

After this, we will merge some of the dev work like
type aliases and inlining into master, so any additional
changes for the Go 1.8 release will need to be cherry-picked,
not merged.

3e55059f cmd/dist: really skip the testsanitizers tests on Android
09496599 runtime: add explicit (void) in C to avoid GCC 7 problem
4cffe2b6 cmd/dist: use the target GOOS to skip the test for issue 18153
6bdb0c11 doc: update go1.8 release notes after TxOptions change
09096bd3 cmd/go: update alldocs after CL 35150
96ea0918 cmd/compile: use CMPWU for 32-bit or smaller unsigned Geq on ppc64{,le}
21a8db1c doc: document go1.7.5

Change-Id: I9e6a30c3fac43d4d4d15e93054ac00964c3ee958