bug#13687: 24.3.50; `read-regexp' should provide regex for symbol at point as defaults

[Jambunathan K]

Spun from 

        http://debbugs.gnu.org/cgi/bugreport.cgi?bug=11095

`read-regexp' should provide regex for symbol at point as one of the
defaults.  This should be the first of defaults while in any of the
progmodes.

I provided a patch which can be seen here:
        
http://debbugs.gnu.org/cgi/bugreport.cgi?msg=32;filename=bug11095-r110503.diff;att=4;bug=11095


The key thing to note is this:  

1. `find-tag-default' (when find-tag-default-function is nil) will pick
    up the symbol at point.

2. When tag is picked as above, surround it with beginning/end-of-symbol
   regexp delimiters and add it to defaults.

In GNU Emacs 24.3.50.3 (i686-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2013-02-11 on debian-6.05
Bzr revision: 111730 rgm@gnu.org-20130211015045-19w1ceor0tkfxc8q
Windowing system distributor `The X.Org Foundation', version 11.0.10707000
System Description:     Debian GNU/Linux 6.0.5 (squeeze)