from Lawrence D'Oliveiro (ldo)
- storage.c: Simplify BLI_dir_contents and make it and its internal subsidiary routines reentrant
- Moved common code for disposal of a struct direntry to new routine BLI_free_filelist in storage.c, and put calls to it in interface_icons.c and filelist.c
- Took out inclusion of BLI_fileops_types.h from BLI_fileops.h and put it explicitly into .c files that need it (which turned out to be only 7 of the 35 files that were including the former)