perf symbols: Add dso__insert_symbol function

The current method for inserting symbols is to use the symbols__insert()
function. However symbols__insert() does not update the dso symbol
cache.  This causes problems in the following scenario:

1. symbol not found at addr using dso__find_symbol

2. symbol inserted at addr using the existing symbols__insert function

3. symbol still not found at addr using dso__find_symbol() because cache isn't
   updated. This is undesired behavior.

The undesired behavior in (3) is addressed by creating a new function,
dso__insert_symbol() to both insert the symbol and update the symbol
cache if necessary.

If dso__insert_symbol() is used in (2) instead of symbols__insert(),
then the undesired behavior in (3) is avoided.

Signed-off-by: Chris Phlipot <cphlipot0@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1462937209-6032-2-git-send-email-cphlipot0@gmail.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>