added X-Archive-Name-Sep header

Annotation:

 Sometimes there might be a problem converting UTF-8 to zips native
 charset(CP866), because it's not 1:1 conversion. So my solution is to
allow
 developers provide their own version of converted filename and pass it
 to mod_zip along with UTF-8 filename which will go straight to Unicode
 path extra field (thanks to tony2001). So separator is a solution that
doesn't
 break current format. And allows passing file name in both formats as
one string.

 Normally we pass:
 CRC32 <size> <path> <filename>\n
 ...
 * <filename> passed to archive as filename w/o conversion
 * UFT-8 flag for filename is set

 tony2001's X-Archive-Charset: <charset> way:
 CRC32 <size> <path> <filename>\n
 ...
 * <filename> is accepted to be UTF-8 string
 * <filename>, converted to <charset> and passed to archive as filename
 * <filename> passed to Unicode path extra field
 * UFT-8 flag for filename is not set

 My X-Archive-Name-Sep: <sep> solution:
 CRC32 <size> <path> <native-filename><sep><utf8-filename>\n
 ...
 * <native-filename> passed to archive as filename w/o conversion
 * <utf8-filename> passed to Unicode path extra field
 * UFT-8 flag for filename is not set

 You just need to provide separator that won't interfere with file
names. I suggest using '/'
 as it is ASCII character and forbidden on most (if not all) platforms
as a part of filename.

 Empty separator string means no UTF-8 version provided. Usefull when we
need to pass only
 names encoded in native charset. It's equal to 'X-Archive-Charset:
native;'.
 Note: Currently it is impossible after '[PATCH] Support for UTF-8 file
names.'(4f61592b)
 because UFT-8 flag (zip_utf8_flag) is set default for templates.
readme fix
Fix: allow one-character filenames
Merge branch 'master' of github.com:devgs/mod_zip
New tip for mod_zip + SSL
Merge pull request #19 from frol/patch-1

New tip for mod_zip + SSL; Fix: allow one-character filenames