mim: run scripts from a specification file

mim: run scripts from a specification file

mim runs scripts from a specification file which can be thought
of as an extremely limited Makefile. Neither make variables nor
dependencies are supported. By default the file 'Mimfile' is read.
An example:

   hello:
      echo hello $1

   clean:
      rm -rf *

The command 'mim' or 'mim hello' will echo 'hello'. Unlike 'make'
arguments after the first are available to the script; they don't
specify additional targets.

mim isn't enabled by default.  Enabling it increases the size of the
binary by about 500 bytes.

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>