Add index entries for open():
buffer size, I/O
I/O control, buffering
line-buffered I/O
unbuffered I/O
diff --git a/Doc/lib/libfuncs.tex b/Doc/lib/libfuncs.tex
index 0506690..ae4af6c 100644
--- a/Doc/lib/libfuncs.tex
+++ b/Doc/lib/libfuncs.tex
@@ -443,7 +443,10 @@
binary file, you should append \code{'b'} to the \var{mode} value
for improved portability. (It's useful even on systems which don't
treat binary and text files differently, where it serves as
- documentation.) The optional \var{bufsize} argument specifies the
+ documentation.)
+ \index{line-buffered I/O}\index{unbuffered I/O}\index{buffer size, I/O}
+ \index{I/O control!buffering}
+ The optional \var{bufsize} argument specifies the
file's desired buffer size: 0 means unbuffered, 1 means line
buffered, any other positive value means use a buffer of
(approximately) that size. A negative \var{bufsize} means to use