SV platform dependency builds

Code conventions used internally by fftw3 (not in API):

LEARN FROM THE MASTERS: read Ken Thompson's C compiler in Plan 9.

   Avoid learning from C++/Java programs.

INDENTATION: K&R, 5 spaces/tab.  In case of doubt, indent -kr -i5.

NAMES: keep them short.  Shorter than you think.  The Bible was written

   without vowels.  Don't outsmart the Bible.

   Common names:

   R       : real type, aka fftw_real

   E       : real type for local variables (possibly extra precision)

   C       : complex type

   sz      : size

   vecsz   : vector size

   is, os  : input/output stride

   ri, ii  : real/imag input (complex data)

   ro, io  : real/imag output (complex data)

   I, O    : real input/output (real data)

   A       : assert

   CK      : check

   S       : solver, defined internally to each solver file

   P       : plan, defined internally to each solver file

   k       : codelet

   X(...)  : used for mangling of external names (see below)

   K(...)  : floating-point constant, in E precision

   If a name is used often and must have the form fftw_foo to avoid

   namespace pollution, #define FOO fftw_foo and use the short name.

   Leave that hungarian crap to MS.  foo_t counts as hungarian: use

   foo instead.  foo is lowercase so that it does not look like a DOS

   program. Exception: typedef struct foo_s {...} foo;  instead of

   typedef struct foo {...} foo;  for C++ compatibility.

NAME MANGLING: use X(foo) for external names instead of fftw_foo.

    X(foo) expands to fftwf_foo or fftw_foo, depending on the

    precision.  (Unfortunately, this is a ugly form of hungarian

    notation.  Grrr...)  Names that are not exported do not need to be

    mangled.

REPEATED CODE: favor a table.  E.g., do not write

    foo("xxx", 1);

    foo("yyy", 2);

    foo("zzz", -1);

    Instead write

      struct { const char *nam, int arg } footab[] = {

	{ "xxx", 1 },

	{ "yyy", 2 },

	{ "zzz", -1 }

      };

    and loop over footab.  Rationale: it saves code space.

    Similarly, replace a switch statement with a table whenever

    possible.

C++: The code should compile as a C++ program. Run the code through

    gcc -xc++ .  The extra C++ restrictions are unnecessary, of

    course, but this will save us from a flood of complaints when

    we release the code.