Fix path.c's function pointer defenitions.

Fix path.c's function pointer defenitions.

int isn't big enough to hold a FILE* / DIR* on some systems, this causes
segfaults in calls that try to use the resulting FILE* / DIR*:

  TESTSUITE: ERR: 'testsuite_rootfs_fopen' [1176160] terminated by signal 11 (Segmentation fault)
  TESTSUITE: ERR: FAILED: testsuite_rootfs_fopen
  FAIL: testsuite/test-testsuite
  ...
  TESTSUITE: ERR: 'loaded_1' [1176166] terminated by signal 11 (Segmentation fault)
  TESTSUITE: ERR: FAILED: loaded_1
  FAIL: testsuite/test-loaded
  ...
  TESTSUITE: ERR: 'from_alias' [1176181] terminated by signal 11 (Segmentation fault)
  TESTSUITE: ERR: FAILED: from_alias
  FAIL: testsuite/test-new-module

For reference on my system:

  sizeof(int) = 4
  sizeof(long) = 8
  sizeof(FILE*) = 8
  sizeof(DIR*) = 8