mesa: Use get_local_param_pointer in glProgramLocalParameters4fvEXT().

mesa: Use get_local_param_pointer in glProgramLocalParameters4fvEXT().

Using the get_local_param_pointer helper ensures that the LocalParams
arrays have actually been allocated before attempting to use them.

glProgramLocalParameters4fvEXT needs to do a bit of extra checking,
but it can be simplified since the helper has already validated the
target.

Fixes crashes in programs that use Cg (for example, Awesomenauts,
Rocketbirds: Hardboiled Chicken, and Tiny and Big: Grandpa's Leftovers)
since commit e5885c119de1e508099cc1111e1c9f8ff00fab88
(mesa: Dynamically allocate the storage for program local parameters.)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=73136
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Brian Paul <brianp@vmware.com>
Tested-by: Laurent Carlier <lordheavym@gmail.com>