fgetstr now works with strings up to SSIZE_MAX as a result, but may
reallocate buffers needlessly just like it used to when the buffer size
exceeds INT_MAX.
fgetstr converts errno EOVERFLOW to EINVAL on getdelim error.
Remove some warnings that only appear on i386 (not on amd64) and that
for some reason best known to others are deemed fatal for i386.
Making this code 'pass lint' does absolutely nothing for its readability (etc).
getdelim works on strings up to SSIZE_MAX and returns -1 on EOF.
__fgetstr is now just a wrapper around __getdelim and ensures that
the buffer doesn't overflow the one provided by FILE.
__slbexpand is now static in fgetwln as it is the only consumer of that func.
