Load cl for using lexical-let*

[syohex]

There are following byte-compile warnings. This change fixes them.

In javap-buffer:
javap-mode.el:88:4:Warning: `(b-name (file-name-nondirectory
    (buffer-file-name)))' is a malformed function
javap-mode.el:90:19:Warning: reference to free variable `b-name'
javap-mode.el:92:39:Warning: reference to free variable `new-b-name'
javap-mode.el:98:41:Warning: reference to free variable `old-buf'
javap-mode.el:100:11:Warning: reference to free variable `new-buf'
javap-mode.el:110:28:Warning: reference to free variable `done'

In end of data:
javap-mode.el:120:1:Warning: the following functions are not known to be defined: lexical-let*,
    b-name, new-b-name, new-buf, old-buf, done