Report 4 pieces of discrepancies between `lineref`s and C source files

[lyazj]

When I try the following command in the main directory of this project:

$ rm -rf latex.out; make $(ls *.tex | sed 's/^/latex.out\//g') >/dev/null

I get the four unexpected error lines:

kernel/fs.c: cannot find pat re.compile('^..if.n.>.0.')
kernel/fs.c: cannot find pat re.compile('panic')
kernel/pipe.c: cannot find pat re.compile('myproc..-\\>killed')
kernel/proc.c: cannot find pat re.compile('DOC: sleeplock0')

Could you please correct the references in your latex files to your C codes to make the impressive book more rigorous?

This check is inspired by spotting an unterminated line on page 95 of the current book:

and if the write has extended the file, writei must update its size