chore, don't build yuck in src/ upon make clean
Merge branch 'bld/flow'

* bld/flow:
  chore, don't build yuck in src/ upon make clean
hygiene, do not deref NULL upon realloc() failure
hygiene, return early when allocation for args fails
hygiene, check for out of bounds fp in xdirname() and bugger off early
chore, protect against deref'ing NULL when realloc() fails
hygiene, only check for NULL ptr after realloc() in bbuf_cat()
hygiene, check return value of bbuf_cpy() before using it
hygiene, insist on non-NULL pointers as arg to __identify()
hygiene, check input to xstrncpy() for NULL pointers
hygiene, check input to __identify(), go back to restricted pointers
hygiene, do away with pointer aliases, use tgt->args in gen'd yuck code
Merge branch 'code/hygiene'

* code/hygiene:
  hygiene, do away with pointer aliases, use tgt->args in gen'd yuck code
  hygiene, check input to __identify(), go back to restricted pointers
  hygiene, check input to xstrncpy() for NULL pointers
  hygiene, insist on non-NULL pointers as arg to __identify()
  hygiene, check return value of bbuf_cpy() before using it
  hygiene, only check for NULL ptr after realloc() in bbuf_cat()
  chore, protect against deref'ing NULL when realloc() fails
  hygiene, check for out of bounds fp in xdirname() and bugger off early
  hygiene, return early when allocation for args fails
  hygiene, do not deref NULL upon realloc() failure