complibs/ppl: update GMP location configuration argument for PPL v0.11 and later

'configure' for PPL 0.11 (and later) needs "--with-gmp-prefix" to
provide the location of the GMP toolkit; the previous switches were
"--with-libgmp-prefix" and "--with-libgmpxx-prefix".

The upstream log message is:

commit 08dfb6fea094f8c5a533575a3ea2095edce99a6d
Author: Roberto Bagnara <bagnara@cs.unipr.it>
Date: Sun Jul 12 21:39:46 2009 +0200

New configure option --with-gmp-prefix supersedes the (now removed)
options --with-libgmp-prefix and --with-libgmpxx-prefix.

Link: http://www.cs.unipr.it/git/gitweb.cgi?p=ppl/ppl.git;a=commit;h=08dfb6fea094f8c5a533575a3ea2095edce99a6d

Since PPL's 'configure' ignores unknown switches, we use all three so we
don't have to conditionalize the ppl.sh build script itself.

Signed-Off-By: Anthony Foiani <anthony.foiani@gmail.com>
(transplanted from 4f0c4fb572e2862c24b28e8d27ce7e9cb9adba65)

# Menu for the cross GDB

config STATIC_TOOLCHAIN

    select GDB_CROSS_STATIC if GDB_CROSS

config GDB_CROSS

    bool

    prompt "Cross-gdb"

    default y

    select GDB_GDBSERVER if ! BARE_METAL

    help

      Build and install a cross-gdb for the target, to run on host.

if GDB_CROSS

config GDB_CROSS_STATIC

    bool

    prompt "Build a static cross gdb"

    default n

    help

      A static cross gdb can be usefull if you debug on a machine that is

      not the one that is used to compile the toolchain.

      That way, you can share the cross-gdb without installing a toolchain

      on every machine that will be used to debug target programs.

endif # GDB_CROSS