If acquiring a lock on the history or uvar file takes more than 250 ms
disable locking of the file. On systems with broken remote file system
locking it can cause tens of seconds delay after running each command
which can make the shell borderline unusable.
This also changes history file locking to use flock() rather than
fcntl() to be consistent with uvar file locking. It also implements the
250 ms time limit before giving up on locking.
Fixes#685
This fixes some of the IWYU and cppcheck lint warnings. And only on
macOS (formerly OS X). Fixing these types of warnings on a broader set
of platforms should be done but this is a baby step to making `make
lint-all` have few, if any, warnings. This reduces the number of lines
in the `make lint-all` output on macOS by over 500 lines.
I found that after fixing the args to `cppcheck` it started reporting
lots of varFuncNullUB warnings. Suppress them as they should be safe to
ignore. Also, improve the readability of the script.
