This patch enables the use of custom hash and comparison functions when 
adding elements to a bcache. The patch also introduces hash and 
comparison functions which take into consideration only the relevant 
properties of the psymbol.

Tested by running the test suit on F13 with gcc 4.4.4 on x8664, no 
regressions.

also used 'main print statistics' to ensure that the bcache object count 
and unique object count are as expected with a small test case.

Sami