RFC 2849 http://tools.ietf.org/html/rfc2849:
SPACE = %x20
; ASCII SP, space
...
2) Any non-empty line, including comment lines, in an LDIF file
MAY be folded by inserting a line separator (SEP) and a SPACE.
Folding MUST NOT occur before the first character of the line.
In other words, folding a line into two lines, the first of
which is empty, is not permitted. Any line that begins with a
single space MUST be treated as a continuation of the previous
(non-empty) line. When joining folded lines, exactly one space
character at the beginning of each continued line must be
discarded. Implementations SHOULD NOT fold lines in the middle
of a multi-byte UTF-8 character.