Merge branch 'rj/sparse'

* rj/sparse:
  sparse: Fix some "symbol not declared" warnings
  sparse: Fix errors due to missing target-specific variables
  sparse: Fix an "symbol 'merge_file' not decared" warning
  sparse: Fix an "symbol 'format_subject' not declared" warning
  sparse: Fix some "Using plain integer as NULL pointer" warnings
  sparse: Fix an "symbol 'cmd_index_pack' not declared" warning
  Makefile: Use cgcc rather than sparse in the check target