[CLN-list] CLN extern "C" patch

[Jan]

Hi,

here is a re-worked version of the patch.

Compilers:
Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 16.00.30319.01
for 80x86 (from the free Studio Express 2010 package)
gcc and g++ (Ubuntu/Linaro 4.4.4-14ubuntu5) 4.4.5

Problem:

> Having an extern "C" variable/function in the namespace scope is allowed
> by the standard. However, there are some limitations which effectively
> deny the purpose of namespaces. That is, according to [dcl.link] 
> 
> "At most one function with a particular name can have C language linkage.
> Two declarations for a function with C language linkage with the same
> function name (ignoring the namespace names that qualify it) that appear
> in different namespace scopes refer to the same function. Two declarations
> for an object with C language linkage with the same name (ignoring
> the namespace names that qualify it) that appear in different namespace
> scopes refer to the same object."
> 
> For instance, in the code below
> 
> namespace A {
> extern "C" int f();
> }
> 
> namespace B {
> extern "C" void f();
> }
> 
> A::f() and B::f() actually refer to the same function! In my opinion it's
> very confusing, and we'd better avoid using extern "C" functions (and
> variables) in the namespace scope.

Second problem:
MSVC has a bug where extern "C" declarations inside a namespace do not
produce the same linker symbol as when they are used outside a
namespace. The linker then produces "unresolved externals" error
messages.

Solution:
Moved the following extern "C" declarations out of the cln namespace and
prefixed them with cln_ :
mulu32_high
mulu64_high
divu_16_rest
divu_32_rest
divu_64_rest

N.B. There are more linker errors with MSVC, but I will address these in
a separate patch.

Best regards,
	Jan

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