debugger: assign Environment to DebugContext too

fix #7517
installer: copy smalloc.h on installation

fix #7485

Signed-off-by: Fedor Indutny <fedor@indutny.com>
doc: correct check for failed child_process.spawn

Since 0.10.x, exec failures are no longer signaled through stderr,
but rather as error events.

Signed-off-by: Fedor Indutny <fedor@indutny.com>
test: remove invalid http test

As a comment in the test states: "This test should not be ported
to v0.10 and higher, because the problem is fixed by not ignoring
ECONNRESET in the first place."

The test is checking whether write returns false instead of
whether an ECONNRESET has been raised.
test: add test-http-destroyed-socket-write2

This test verifies that ECONNRESET is raised when writing to an
http request where the server has destroyed the socket.