[plt-scheme] FFI and ARM

drscheme 352 builds and seems to run nicely out of the box on my shiny
new Nokia N800, except that foreign.c compilation fails for the ARM
target (i.e. the unit itself rather than an emulation dev env) thus:

./foreign.c:2133: error: syntax error before "ffi_closure"
./foreign.c:2133: warning: no semicolon at end of struct or union
./foreign.c:2140: error: syntax error before '}' token
./foreign.c:2140: warning: type defaults to `int' in declaration of `closure_and_cif'
./foreign.c:2140: warning: data definition has no type or storage class
./foreign.c: In function `foreign_ffi_callback':
./foreign.c:2199: error: `ffi_closure' undeclared (first use in this function)
./foreign.c:2199: error: (Each undeclared identifier is reported only once
./foreign.c:2199: error: for each function it appears in.)
./foreign.c:2199: error: `cl' undeclared (first use in this function)
./foreign.c:2200: error: `cl_cif_args' undeclared (first use in this function)
./foreign.c:2239: warning: implicit declaration of function `ffi_prep_closure'

Looking at the FFI code, there doesn't seem to be an ARM directory,
which presumably explains it!  Could this be sorted out easily?

John