Do not insert line breaks into function/event/hook definitions if they fit on a single line

[bbannier]

As of zeek-format-1.1.0 definitions of e.g., events without body or with one-statement bodies always inserts a line break. Instead I would have expected no line break, at least in the case where there is no body (one could argue that with a body forcing a line break is good).

Example:

# Start point:
event zeek_init() {}

# Is formatted as:
event zeek_init()
{ } # Note forced ` ` in body.