crypto/tls: force OS X target version to 10.6 for API compatibility
crypto/tls: force OS X target version to 10.6 for API compatibility

This is a band-aid until we can use weak imports with cgo.

Fixes issue 3131.

R=minux.ma, rsc
CC=golang-dev
http://codereview.appspot.com/5700083

Committer: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

dsriram/golang,dsriram/golang,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,gnanderson/go,gnanderson/go,gnanderson/go,dsriram/golang,pombredanne/go-deleteme,gnanderson/go,tv42/old-go,gnanderson/go,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,apparentlymart/golang,dsriram/golang,pombredanne/go-deleteme,apparentlymart/golang,apparentlymart/golang,pombredanne/go-deleteme,dsriram/golang,dsriram/golang,pombredanne/go-deleteme,gnanderson/go,tv42/old-go,apparentlymart/golang,apparentlymart/golang,gnanderson/go,apparentlymart/golang,apparentlymart/golang,dsriram/golang,pombredanne/go-deleteme