Allow multi-word "install" command.

Autoconf can determine that the correct install command includes flags,
e.g., "/usr/bin/install -c". When using this as a command, we can't
enclose the value in double-quotes, as that makes some shells use the
whole expression as a filename:

# this is the value returned by autoconf and stored in CT_install
$ ins="/usr/bin/install -c"

# if we call it with quotes, the command is not found
$ "${ins}"
bash: /usr/bin/install -c: No such file or directory

# removing the quotes lets it work as expected
$ ${ins}
/usr/bin/install: missing file operand
Try `/usr/bin/install --help' for more information.

Signed-Off-By: Anthony Foiani <anthony.foiani@gmail.com>

# MPC options

choice

    bool

    prompt "MPC version"

# Don't remove next line

# CT_INSERT_VERSION_BELOW

config MPC_V_0_9

    bool

    prompt "0.9 (EXPERIMENTAL)"

    depends on EXPERIMENTAL

config MPC_V_0_8_2

    bool

    prompt "0.8.2 (EXPERIMENTAL)"

    depends on EXPERIMENTAL

config MPC_V_0_8_1

    bool

    prompt "0.8.1"

config MPC_V_0_7

    bool

    prompt "0.7"

config MPC_V_0_6

    bool

    prompt "0.6 (OBSOLETE)"

    depends on OBSOLETE

endchoice

config MPC_VERSION

    string

# Don't remove next line

# CT_INSERT_VERSION_STRING_BELOW

    default "0.9" if MPC_V_0_9

    default "0.8.2" if MPC_V_0_8_2

    default "0.8.1" if MPC_V_0_8_1

    default "0.7" if MPC_V_0_7

    default "0.6" if MPC_V_0_6