pgsql: Fix config file lexer to not barf if postgresql.conf ends with a

Log Message:
-----------
Fix config file lexer to not barf if postgresql.conf ends with a comment
that has no terminating newline. Per report from maps.on at gmx.net.

Modified Files:
--------------
pgsql/src/backend/utils/misc:
guc-file.l (r1.30 -> r1.31)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc-file.l.diff?r1=1.30&r2=1.31)