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>

 Index: ltrace-0.5.3/configure

 ===================================================================

 --- ltrace-0.5.3/configure

 +++ ltrace-0.5.3/configure

 @@ -78,7 +78,10 @@ fi

  rm -f conftest.c a.out

  CFLAGS='-g -O2'

 -LIBS='-lelf -lsupc++ -liberty '

 +LIBS='-lelf'

 +[ -n "$HAVE_LIBSUPC__" ] && LIBS="$LIBS -lsupc++"

 +[ -n "$HAVE_LIBIBERTY" ] && LIBS="$LIBS -liberty"

 +

  INSTALL='install -c'

  iquote='-iquote '

  iquoteend=''