command_util.bash: Kill make_proto().

It is always a bad idea to parse C code with a regex in a script. In
addition, it is completely unnecessary in this case.

This commit changes command_util.bash to define, in addition to the
old XXX_CMD_ARRAY, another preprocessor macro XXX__COMMAND_HANDLERS
containing the comma separated list of command handlers without
any type information instead of grepping the source files. A simple
typedef is used to declare all command handlers.

Avoiding all the grep/sed calls reduces the (warm cache) make dep
time by ~10%.