Check for `< 0` instead of `== -1`.

Fixes coding style. Formatting commits suck, incoherent coding style
sucks more.
https://suckless.org/coding_style/

Fixes coding style. Formatting commits suck, incoherent coding style
sucks more.
https://suckless.org/coding_style/

Except stated otherwise in comment.

Fixes coding style. Formatting commits suck, incoherent coding style
sucks more.
https://suckless.org/coding_style/

Long, wrapped, multi-line if statements suck to read.
This fixes readability in the worst places by packing format strings for
paths into defines.

function prototype with unspecified argument is obsolete since c99.

additionally some of these function which don't take any argument were
being called with a `const char *` arg, which is UB.

fix both these issues by declararing ALL the components to accept a
`const char *`, and name the arg "unused" if it's meant to be ignored.

this gives the compiler a chance to check weather the prototype and
definiton matches or not, which would catch issues like 3c47701.