more -Wall warning fixes from Cristian Ionescu-Idbohrn.
This time it resulted in small code changes:

function                                             old     new   delta
nexpr                                                820     828      +8
tail_main                                           1200    1202      +2
wrapf                                                166     167      +1
parse_mount_options                                  227     209     -18
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(add/remove: 0/0 grow/shrink: 3/1 up/down: 11/-18)             Total: -7 bytes

27 files changed