build: use AM_SILENT_RULES conditionally

It's not supported by older automake versions.
build: add DTrace detection for autotools
linux,darwin,win: link-local IPv6 addresses

Modified uv_ip6_addr() to fill sin6_scope_id for link-local addresses.

Fixes #271

Conflicts:
	build.mk
unix: fix build when !defined(PTHREAD_MUTEX_ERRORCHECK)

Ancient versions of glibc (<= 2.3.1) don't have error-checking mutexes.
Merge remote-tracking branch 'origin/v0.10'