MSVC patch: export symbol

[Michael Goffioul]

The following patch is needed in order to compile language packages
(at least pt_BR needs it).

Michael.

Index: src/help.h
===================================================================
RCS file: /cvs/octave/src/help.h,v
retrieving revision 1.24
diff -c -p -r1.24 help.h
*** src/help.h  17 Jan 2007 21:47:51 -0000  1.24
--- src/help.h  1 Jun 2007 08:08:58 -0000
*************** extern void display_usage_text (std::ost
*** 39,45 ****

 extern void additional_help_message (std::ostream&);

! extern std::string raw_help (const std::string&, bool&);

 // Name of the info file specified on command line.
 // (--info-file file)
--- 39,45 ----

 extern void additional_help_message (std::ostream&);

! extern OCTINTERP_API std::string raw_help (const std::string&, bool&);

 // Name of the info file specified on command line.
 // (--info-file file)