path: add 'garray.h' to headers

The function prototypes use garray_T* arguments, but the header is not
included in path.h. Technically we could also get away with a forward
declaration since we're just using the pointer, but I don't see the urgent
need for that.

src/path.h

@@ -3,6 +3,7 @@
 
 #include "func_attr.h"
 #include "types.h"
+#include "garray.h"
 
 /// Return value for the comparison of two files. Also @see path_full_compare.
 typedef enum file_comparison {