c++ patch

[Torbjorn Granlund]

Back in May, Marc Glisse <marc.glisse at normalesup.org> writes:

  I attach a patch that I am using. It in particular helps me on
  solaris, where I use:
  CC=cc
  CXX=CC
  ABI=32
  CXXFLAGS=-library=stlport4
  
  Some cxx tests (t-binary t-ops t-prec t-ternary t-unary) still fail to
  compile, but I believe it is because of bugs in the compiler (whereas
  what I patched looks like bugs in the code).
  
  A bit more details:
  there are a number of missing std:: for c++ use. Since gmp-impl.h is
  not installed, it can just use the easy "using namespace std;". For
  gmp.h, I did something cleaner (It is better for standard conformance,
  but I am not sure it may not hurt some broken c++ compiler).
  The typedef in gmpxx.h is because a C linkage function and a C++
  linkage function need not look the same I think.
  
  
[long patch snipped]

I wonder if we need to support every C++ compiler with gmp.h.  If C++
doesn't provide the size_t type, I think we will re-introduce
incompatibilities with those compilers, whenever we hack gmp.h.

Perhaps we should instead declare exactly what gmpxx.h needs from
gmp.h, in gmpxx.h, in a syntax every C++ compiler might understand?
The only thing we need, are prototypes for the C functions used from
gmpxx.h, right?

-- 
Torbjörn