Make utf16_create_file static and update prototype.

Closes #183
diff --git a/lib/zip_source_file_win32_utf16.c b/lib/zip_source_file_win32_utf16.c
index 8d48550..563f924 100644
--- a/lib/zip_source_file_win32_utf16.c
+++ b/lib/zip_source_file_win32_utf16.c
@@ -34,7 +34,7 @@
 #include "zip_source_file_win32.h"
 
 static char *utf16_allocate_tempname(const char *name, size_t extra_chars, size_t *lengthp);
-static HANDLE __stdcall utf16_create_file(const void *name, DWORD access, DWORD share_mode, PSECURITY_ATTRIBUTES security_attributes, DWORD creation_disposition, DWORD file_attributes, HANDLE template_file);
+static HANDLE __stdcall utf16_create_file(const char *name, DWORD access, DWORD share_mode, PSECURITY_ATTRIBUTES security_attributes, DWORD creation_disposition, DWORD file_attributes, HANDLE template_file) {
 static void utf16_make_tempname(char *buf, size_t len, const char *name, zip_uint32_t i);
 static char *utf16_strdup(const char *string);
 
@@ -78,7 +78,7 @@
 }
 
 
-HANDLE __stdcall
+static HANDLE __stdcall
 utf16_create_file(const char *name, DWORD access, DWORD share_mode, PSECURITY_ATTRIBUTES security_attributes, DWORD creation_disposition, DWORD file_attributes, HANDLE template_file) {
 #ifdef MS_UWP
     CREATEFILE2_EXTENDED_PARAMETERS extParams = {0};