Fix for building with Visual Studio 2008 Express (link error to be pr…

…ecise)

I needed to add 1 define in 3 files, betweend #if defined(_WIN32) guards :
- #define strncasecmp	_strnicmp
- #define snprintf	_snprintf

src/sundown/autolink.c

@@ -21,6 +21,10 @@
 #include <stdio.h>
 #include <ctype.h>
 
+#if defined(_WIN32)
+#define strncasecmp _strnicmp
+#endif
+
 int
 sd_autolink_issafe(const uint8_t *link, size_t link_len)
 {

src/sundown/html_smartypants.c

@@ -22,6 +22,10 @@
 #include <stdio.h>
 #include <ctype.h>
 
+#if defined(_WIN32)
+#define snprintf _snprintf 
+#endif
+
 struct smartypants_data {
  int in_squote;
  int in_dquote;

src/sundown/markdown.c

@@ -25,6 +25,10 @@
 #include <ctype.h>
 #include <stdio.h>
 
+#if defined(_WIN32)
+#define strncasecmp _strnicmp
+#endif
+
 #define REF_TABLE_SIZE 8
 
 #define BUFFER_BLOCK 0