Sync with FreeBSD. Notable changes:

Sync with FreeBSD.  Notable changes:

Kill extraneous whitespace.

Flush streams before calling system() so that the output appears in the
right place in the output stream when redirected to a file (when full
buffering is enabled).

Store a pointer to "null" in struct ndblock's defn member instead of a
duplicate allocated on the heap; the address defn points to is significant,
and is checked against the address of "null" in certain conditionals.

Fix m4 to properly handle bitwise operators &, ^, and |. Fix operator
precedence. Add short-circuit evaluation.

Respect locale settings from the environment.

Add a new m4 script to test the functionality of math operators in eval().