bashrc: use xterm as default terminal

* this fixes apps like nano not working from a bash shell

Change-Id: I92e22f845172e63abb5abb3567c1447041e977d5
Patch cve-2014-6271

Patch-ID: bash30-017
Under certain circumstances, bash will execute user code while processing the
environment for exported function definitions.

Change-Id: Iccac7b4ae914354978079783a9fe50b3b38ddad5
Patch CVE-2014-7169

Patch-ID: bash41-013
Under certain circumstances, bash can incorrectly save a lookahead character and
return it on a subsequent call, even when reading a new line.

Change-Id: I29dcf444011f77e104b6a82e8cada731e3917646
ref: http://seclists.org/oss-sec/2014/q3/734
ref: http://seclists.org/oss-sec/2014/q3/685