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>

 Original patch from gentoo: gentoo/src/patchsets/gcc/4.3.1/uclibc/90_all_303-c99-complex-ugly-hack.patch

 diff -durN gcc-4.3.1.orig/libstdc++-v3/configure gcc-4.3.1/libstdc++-v3/configure

 --- gcc-4.3.1.orig/libstdc++-v3/configure	2008-06-10 14:58:43.000000000 +0200

 +++ gcc-4.3.1/libstdc++-v3/configure	2008-06-10 14:58:58.000000000 +0200

 @@ -39006,6 +39006,9 @@

  cat >>conftest.$ac_ext <<_ACEOF

  /* end confdefs.h.  */

  #include <complex.h>

 +#ifdef __UCLIBC__

 +#error ugly hack to make sure configure test fails here for cross until uClibc supports the complex funcs

 +#endif

  int

  main ()

  {