This commit converts the dependency management from Godeps to the vendor
folder, also switching the tool from godep to trash. Since the upstream tool
lacks a few features proposed via a few PRs, until those PRs are merged in
(if), use github.com/karalabe/trash.

You can update dependencies via trash --update.

All dependencies have been updated to their latest version.

Parts of the build system are reworked to drop old notions of Godeps and
invocation of the go vet command so that it doesn't run against the vendor
folder, as that will just blow up during vetting.

The conversion drops OpenCL (and hence GPU mining support) from ethash and our
codebase. The short reasoning is that there's noone to maintain and having
opencl libs in our deps messes up builds as go install ./... tries to build
them, failing with unsatisfied link errors for the C OpenCL deps.

golang.org/x/net/context is not vendored in. We expect it to be fetched by the
user (i.e. using go get). To keep ci.go builds reproducible the package is
"vendored" in build/_vendor.

Fixes #3203

Update goleveldb, add debug.chaindbCompact

eth/downloader: fix a data race in a log output

cmd/geth, code, eth/downloader: tune import logs and mem stats

cmd/geth, trie: report on trie cache unloads, also add debug log

cmd, core/state: allow configurable trie cache generations

core/vm: fix GASPRICE string (resolves #2553)

trie: improve cache unloading mechanism

cmd/geth, trie: track and report trie cache misses

The pending state was not copied while not mining, leading to a data race.

core: Add block processing time metric collection

cmd/geth: compact and print database stats after an import

common, core, eth/downloader: adjust import log formatting

This was caught by the new invariant check.

Commit 40cdcf11 broke the optimisation which kept nodes resolved
during Get in the trie. The decoder assigned cache generation 0
unconditionally, causing resolved nodes to get flushed on Commit.

This commit fixes it and adds two tests.

New checks whether the root node is present by loading it from the
database. Keep the node around instead of discarding it.

	internal/ethapi, internal/web3ext: adds raw tx retrieval methods

trie: fix regression that linked all downloaded nodes together

params: set reprice block number to 2463000

The trie sync code links subtries using pointers into node structs.
Since commit 40cdcf11 nodes are no longer copied when unpacking from
an interface value, causing all nodes to get linked up as the sync
progresses. Fix it by breaking the pointer chain with an explicit copy.

core, core/vm: added gas price variance table (EIP #150)

core: add global (soft) limits on the pending transactions