mark all functions in headers with VIS_EXPORT or VIS_INTERNAL

if vis actually wants to be a library exported symbols may need
mark up depending on the platform (eg. __declspec(dllexport)).
This needs to be hidden behind a macro because the way you export
is not the same on every platform.

I did this based on the assumption that vis.h was supposed to be
the only interface to the "vis" library. Since nobody actually
uses vis as a library I have no idea if this is actually correct.

Anyway marking up all prototypes like this allows for one to
convert all functions to static if a single translation unit is
used by inserting at the start:

 #define VIS_INTERNAL static
 #define VIS_EXPORT   static

1 files changed, 2 insertions, 2 deletions

diff --git a/libutf.h b/libutf.h
index a2b81b7..30255cc 100644
--- a/libutf.h
+++ b/libutf.h
@@ -28,7 +28,7 @@ typedef unsigned long Rune;
 #define Runeself 0x80             /* rune and utf are equal (<) */
 #define Runemax  RUNE_C(0x10FFFF) /* maximum rune value */
 
-int runelen(Rune r);
-int runetochar(char *s, const Rune *p);
+VIS_INTERNAL int runelen(Rune r);
+VIS_INTERNAL int runetochar(char *s, const Rune *p);
 
 #endif