<rdar://problem/13178743>

Added a new "env" regular expression alias. If "env" is typed on its own "settings show target.env-vars" will be run. Otherwise it can be used to set and environment variable: "env FOO=BAR".



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@174991 91177308-0d34-0410-b5e6-96231b3b80d8