bug#39432: Long line issue in sed 4.8

[Paul Fox]

Seems there are bugs in sed handling long lines. You can reproduce by:

1. generate file > 2GB - must be a single line.
2. sed -e s/xxx/yyy/ <file

The search expression doesn't matter whether it matches or not. Using a
file filled with "The quick brown fox..." (no newlines), sed aborts saying
something like:

reg_exp: INT_MAX overflow

Prior versions of sed incorrectly handled ck_getline to read very long
lines (int vs size_t). Whilst that was fixed, subsequent code trips over
with lengths being put into int's.

If anyone needs more info - let me know. I did run sed under gdb to
diagnose, at my work area. But likely I can reproduce from this machine.

(Not critical issue)