whitespace fixes and asterisk placement
fixed several memory leaks and bugs

expr_free is GDestroyNotify compatible--casts void* to expr_s*
scaffolding GSLists in supervisor_run are correctly g_slist_free_full'd
expr_join doesn't allocate a new GString and simply overwrites source
  arg like strcat
op_add uses new expr_join and doesn't leak old a_expr by overwriting ptr
op_add doesn't leak throwaway GString to expr_join a '+', changed to
  g_string_append_c
op_add doesn't stupidly use free instead of eg_free and make check_mem_leak
  declare a leaked pointer that valgrind then can't detect!!
replaced now unnecessary stdlib.h include in op_add with mem_wrap
total bytes saved: 1148
replaced error report in check_mem_leak with simple ptr count
prune includes in supervisor and future comment notes in expr