Escape # when first character in log file line

[amannb]

Bro should probably escape the # character, when it is the first that appears in a line and when the header fields are used.

Example output:

#separator \x09
#set_separator	,
#empty_field	(empty)
#unset_field	-
#path	test
#fields	status
#types	string
#test

Script to generate output is attached.