Files: add wrappers for certain open() methods

Due to filepath encoding issues on win32 we need
wrappers for:
- open()
- fopen()
- opendir()
- zip_open() (this is readonly on win32)

Patch only declares/defines the wrappers
in dive.h, windows.c, linux.c, macos.c.

Suggestions-by: Thiago Macieira <thiago@macieira.org>
Suggestions-by: Jef Driesen <jefdriesen@telenet.be>
Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

linux.c

@@ -6,6 +6,8 @@
 #include <sys/types.h>
 #include <dirent.h>
 #include <fnmatch.h>
+#include <stdio.h>
+#include <fcntl.h>
 
 const char system_divelist_default_font[] = "Sans 8";
 
@@ -97,3 +99,29 @@ int enumerate_devices (device_callback_t callback, void *userdata)
 
 	return index;
 }
+
+/* NOP wrappers to comform with windows.c */
+int subsurface_open(const char *path, int oflags, mode_t mode)
+{
+	return open(path, oflags, mode);
+}
+
+FILE *subsurface_fopen(const char *path, const char *mode)
+{
+	return fopen(path, mode);
+}
+
+void *subsurface_opendir(const char *path)
+{
+	return (void *)opendir(path);
+}
+
+struct zip *subsurface_zip_open_readonly(const char *path, int flags, int *errorp)
+{
+	return zip_open(path, flags, errorp);
+}
+
+int subsurface_zip_close(struct zip *zip)
+{
+	return zip_close(zip);
+}