Dive pictures: Move metadata functions into own translation unit

Move all metadata function into new core/metadata.cpp file.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/metadata.h

@@ -0,0 +1,31 @@
+#ifndef METADATA_H
+#define METADATA_H
+
+#include "units.h"
+
+struct metadata {
+	timestamp_t	timestamp;
+	degrees_t	latitude;
+	degrees_t	longitude;
+};
+
+enum mediatype_t {
+	MEDIATYPE_IO_ERROR,	// Couldn't read file
+	MEDIATYPE_UNKNOWN,	// Couldn't identify file
+	MEDIATYPE_PICTURE,
+	MEDIATYPE_VIDEO,
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+enum mediatype_t get_metadata(const char *filename, struct metadata *data);
+timestamp_t picture_get_timestamp(const char *filename);
+void picture_load_exif_data(struct picture *p);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // METADATA_H