indenting preprocessor conditionals?

[John W. Eaton]

Are there any preferences for indenting preprocessor conditionals?  If 
there are no objections, I'd like to start writing something like

#if defined (HAVE_SUITESPARSE_AMD_H)
# include <suitesparse/amd.h>
#elif defined (HAVE_UFSPARSE_AMD_H)
# include <ufsparse/amd.h>
#elif defined (HAVE_AMD_AMD_H)
# include <amd/amd.h>
#elif defined (HAVE_AMD_H)
# include <amd.h>
#endif

or

#if defined (HAVE_CXSPARSE)
# if defined (ENABLE_64)
#  define CXSPARSE_DNAME(name) cs_dl ## name
#  define CXSPARSE_ZNAME(name) cs_cl ## name
# else
#  define CXSPARSE_DNAME(name) cs_di ## name
#  define CXSPARSE_ZNAME(name) cs_ci ## name
# endif
#endif

instead of smashing everything over on the left margin.

Indentation increments of one space seem common for this kind of thing, 
but maybe we should go with two since that's generally the amount we use 
in other code in Octave.

I've also seen

#if defined (HAVE_CXSPARSE)
  #if defined (ENABLE_64)
    #define CXSPARSE_DNAME(name) cs_dl ## name
    #define CXSPARSE_ZNAME(name) cs_cl ## name
  #else
    #define CXSPARSE_DNAME(name) cs_di ## name
    #define CXSPARSE_ZNAME(name) cs_ci ## name
  #endif
#endif

though I think I prefer to leave the '#' character in the first column.

Note that I would NOT apply the indentation to anything inside the 
multiple inclusion guards, so we would still have

#if !defined (octave_foo_h)
#define octave_foo_h 1

#include <iostream>
...

#endif

Comments?

jwe