postprocess: handle partial intialization failures.

postprocess: handle partial intialization failures.

This patch fixes segfaults observed when enabling the post processing
features. When the format is not supported, or a texture cannot be
created, the code must gracefully handle failure and report the error to
the calling code for proper failure handling.

To accomplish this the following changes were made to the filters.h
prototypes:

- bool return for pp_init_func
- Added pp_free_func for filter specific resource destruction

Fixes segfaults from backtraces:

* util_destroy_blit
  pp_free

* u_transfer_inline_write_vtbl
  pp_jimenezmlaa_init_run
  pp_init

This patch also uses tgsi_alloc_tokens to allocate temporary tokens in
pp_tgsi_to_state, instead of allocating the array on the stack. This
fixes the following stack corruption segfault in pp_run.c:

* _int_free
  aaline_delete_fs_state
  pp_free

Bug Number: 1021843
Reviewed-by: Brian Paul <brianp@vmware.com>