Fixes sharedmethod to work on Python 2.6.
Fixes sharedmethod to work on Python 2.6.

My original workaround to this involved pulling out the get_function
helper function defined in deprecated and using that in place of
self.__func__.  But I needed a few other things for sharedmethod to work
and adding hacks to get_function to support it was starting to look
silly.

So instead this adds a __func__ attribute to shared method, like it
would have on other Python versions, which is crafted to work
transparently the same as other Python versions at the (acceptable) cost
of a little extra overhead (on Python 2.6 only--no overhead is added for
other Python versions).

dhomeier/astropy,astropy/astropy,saimn/astropy,MSeifert04/astropy,tbabej/astropy,dhomeier/astropy,larrybradley/astropy,larrybradley/astropy,StuartLittlefair/astropy,joergdietrich/astropy,stargaser/astropy,kelle/astropy,lpsinger/astropy,tbabej/astropy,pllim/astropy,bsipocz/astropy,tbabej/astropy,joergdietrich/astropy,funbaker/astropy,saimn/astropy,saimn/astropy,StuartLittlefair/astropy,lpsinger/astropy,stargaser/astropy,funbaker/astropy,lpsinger/astropy,pllim/astropy,mhvk/astropy,kelle/astropy,DougBurke/astropy,bsipocz/astropy,mhvk/astropy,astropy/astropy,MSeifert04/astropy,DougBurke/astropy,AustereCuriosity/astropy,kelle/astropy,StuartLittlefair/astropy,mhvk/astropy,mhvk/astropy,funbaker/astropy,mhvk/astropy,saimn/astropy,aleksandr-bakanov/astropy,AustereCuriosity/astropy,dhomeier/astropy,larrybradley/astropy,stargaser/astropy,AustereCuriosity/astropy,pllim/astropy,aleksandr-bakanov/astropy,dhomeier/astropy,lpsinger/astropy,saimn/astropy,StuartLittlefair/astropy,DougBurke/astropy,pllim/astropy,MSeifert04/astropy,joergdietrich/astropy,larrybradley/astropy,astropy/astropy,aleksandr-bakanov/astropy,tbabej/astropy,kelle/astropy,astropy/astropy,pllim/astropy,joergdietrich/astropy,bsipocz/astropy,aleksandr-bakanov/astropy,AustereCuriosity/astropy,funbaker/astropy,DougBurke/astropy,StuartLittlefair/astropy,AustereCuriosity/astropy,MSeifert04/astropy,dhomeier/astropy,stargaser/astropy,lpsinger/astropy,tbabej/astropy,kelle/astropy,larrybradley/astropy,astropy/astropy,joergdietrich/astropy,bsipocz/astropy