sql: infer constraints on equality columns in one-sided joins

Issue cockroachdb#20765 points out an interesting case:
  `SELECT * FROM l LEFT JOIN r USING(a) WHERE a=3`

In this case, `WHERE a=3` is internally `WHERE l.a=3`. We can push
down a corresponding constraint `r.a=3` because only those rows can
contribute to any final results.

In general, for LEFT JOINs we remap any constraints on left-side
equality columns and push them down to the right side. The case for
RIGHT JOINs is symmetric.

Fixes cockroachdb#20765.

Merge pull request cockroachdb#20578 from tschottdorf/table-stats-tim…

…eout

server: bump timeout in TableStats

Merge pull request cockroachdb#20578 from tschottdorf/table-stats-tim…

…eout

server: bump timeout in TableStats

Merge pull request cockroachdb#20491 from tschottdorf/trace-schema-ch…

…anger

sql: trace schema changes

Merge pull request cockroachdb#20264 from knz/20171126-rename-vars

sql: name the transaction settings like PG does

Merge pull request cockroachdb#20209 from mberhault/marc/cherrypick_2…

…0194

cherrypick-1.1: metrics: write vars to temporary buffer.

publish-artifacts: disable source archive generation

Over-the-shoulder code reviewed by @benesch.

deps: constrain go-ole to master to fix Windows builds

The last release of go-ole, v1.2, was two years ago. go-sigar, via
StackExchange/wmi, understandably depends on features added in the last
two years when compiling for Windows.

Fix the Windows build by forcing `dep` to vendor go-ole's master branch
instead of v1.2.

Merge pull request cockroachdb#19585 from jordanlewis/cp-ren-random-uuid

cherrypick-1.1: sql: add builtin function for random UUID generation

Merge pull request cockroachdb#19287 from benesch/1.1-dont-panic

cherrypick-1.1: util/log: don't panic