[tcsh] history pollution

[Olivier Mengué]

tcsh has an history handling bug that makes the current implementation (f88f0ee) pollute the interactive shell history with lines that part of our shell code:

• every time the prompt is displayed two entries are injected in the history: endif and angel leave
• every time the user runs the angel controller the history is polluted with 20 entries (all the lines of the switch statement except the first one)
  This bug makes angel-PS1 unusable with tcsh.

tcsh versions:

• Ubuntu 12.04: tcsh 6.17.06 (Astron) 2011-04-15 (i686-intel-linux) options wide,nls,dl,al,kan,rh,nd,color,filec

[Olivier Mengué]

Reproduced with latest tcsh release:

tcsh 6.18.01 (Astron) 2012-02-14 (i686-intel-linux) options wide,nls,dl,al,kan,rh,color,filec

Issue opened at tcsh.org: #259