allow to change local files

- fuse/filecache:
     * add filecache_upload_patch
     * allow opening files in modes other than RDONLY
 - fuse/hashtbl:
     * add folder_tree_upload_patch
 - fuse/operations:
     * allow opening files in modes other than RDONLY
     * add members to private context which allow tracking of
       not-yet-uploaded files and files opened for writing and
       files opened in read-only mode
 - mfapi/apicalls/upload_patch:
     * supply x-filename and x-filesize headers
 - mfapi/apicalls/upload_simple:
     * do not supply the x-filehash header as it is not used by the
       server
 - utils/hash:
     * hex characters must be lower case for the server
 - utils/strings:
     * clean up unused functions strdup_join, strdup_substr,
       string_chomp
 - utils/stringv:
     * complete rewrite with different string vector implementation

fuse/operations.h

@@ -24,6 +24,7 @@
 #include <sys/types.h>
 #include "../mfapi/mfconn.h"
 #include "hashtbl.h"
+#include "../utils/stringv.h"
 
 struct mediafirefs_context_private {
     mfconn         *conn;
@@ -31,12 +32,14 @@ struct mediafirefs_context_private {
     char           *configfile;
     char           *dircache;
     char           *filecache;
-    /* stores all currently open temporary files which are to be uploaded when
-     * they are closed.
-     * we use a normal array because the number of open temporary files will
-     * never be very high but is limited by the number of threads */
-    char          **tmpfiles;
-    size_t          num_tmpfiles;
+    /* stores:
+     *  - all currently open temporary files which are to be uploaded when
+     *    they are closed.
+     *  - all files that are opened for writing
+     */
+    stringv        *sv_writefiles;
+    /* stores all files that have been opened for reading only */
+    stringv        *sv_readonlyfiles;
 };
 
 int             mediafirefs_getattr(const char *path, struct stat *stbuf);