This ensures 'make test' finds all errors that remote CI would find.
Go 1.7 vet reports a false positive in package log, add a workaround.

This fixes a recent bug where 'make geth' built everything instead of
just geth.

pow: fix Search with ethash test mode

all: import "context" instead of "golang.org/x/net/context"

There is no need to depend on the old context package now that the
minimum Go version is 1.7. The move to "context" eliminates our weird
vendoring setup. Some vendored code still uses golang.org/x/net/context
and it is now vendored in the normal way.

This change triggered new vet checks around context.WithTimeout which
didn't fire with golang.org/x/net/context.

* les: implement request distributor, fix blocking issues
* core: moved header validation before chain mutex lock

build: require Go >= 1.7

We don't use the opencl build tag anymore.

We have decided to bump the requirement to Go 1.7 because it enables
subtests and allows dropping backwards-compatibility code. This is in
line with Go's support policy. Go 1.6 and earlier no longer receive
security updates.

core/types: use gencodec for JSON marshaling code

travis: switch to cocoapods 1.2.0 stable

ethstats: try both ws:// and wss:// if none specified

The cache/dataset methods crashed with a nil pointer error if
cachesinmem/dagsinmem were zero. Fix it by skipping the eviction logic
if there are no caches/datasets.

Search always used the regular dataset size regardless of test mode. Fix
it by removing the redundant size parameter of hashimotoFull.

Fixes #3784

Fixes #3762.  Details about parameter:
https://github.com/rs/cors/blob/a62a804a8a009876ca59105f7899938a1349f4b3/cors.go#L50-L54

light: added new CHT

* main,import: Add --nocompaction flag + multiple import files

* geth/import: documentation

* import: Added more info to err message

* fix :P

mobile: Fix typo ( Ethereun -> Ethereum )