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/filecache.h

@@ -23,6 +23,11 @@ int             filecache_open_file(const char *quickkey,
                                     uint64_t local_revision,
                                     uint64_t remote_revision, uint64_t fsize,
                                     const unsigned char *fhash,
-                                    const char *filecache, mfconn * conn);
+                                    const char *filecache, mfconn * conn,
+                                    mode_t mode, bool update);
+
+int             filecache_upload_patch(const char *quickkey,
+                                       uint64_t local_revision,
+                                       const char *filecache, mfconn * conn);
 
 #endif