Bugzilla

Apparently there are some C++ compilers that have an issue with, for example:
```
void foo(int) {}

class bar {
  decltype(foo)* foo;
};
```
Other compilers (such as the ones I tested with) do not.

So to avoid this inconsistency in com, we're going to have to change our macro that defines these function pointers from
```
#define CUPS_SHIM_FUNC_DECL(X) decltype(X)* X;
```
to
```
#define CUPS_SHIM_FUNC_DECL(X) decltype(::X)* X;
```
so that we are explicit about `decltype`ing from the globally scoped function that exists in `cups.h`

I believe that should fix the issue.

Apparently there are some C++ compilers that have an issue with, for example:
```
void foo(int) {}

class bar {
  decltype(foo)* foo;
};
```
Other compilers (such as the ones I tested with) do not.

So to avoid this inconsistency in com, we're going to have to be explicit about the global scope. 
To fix the example, this would mean:
```
  decltype(::foo)* foo;
```
To fix this code, we'll have to change the declaration macro from
```
#define CUPS_SHIM_FUNC_DECL(X) decltype(X)* X;
```
to
```
#define CUPS_SHIM_FUNC_DECL(X) decltype(::X)* X;
```
so that we are explicit about `decltype`ing from the globally scoped function that exists in `cups.h`

I believe that should fix the issue.

Apparently there are some C++ compilers that have an issue with, for example:
```
void foo(int) {}

class bar {
  decltype(foo)* foo;
};
```
Other compilers (such as the ones I tested with) do not.

So to avoid this inconsistency in compilers, we're going to have to be explicit about the global scope. 

To fix the example, this would mean:
```
  decltype(::foo)* foo;
```
To fix this code, we'll have to change the declaration macro from
```
#define CUPS_SHIM_FUNC_DECL(X) decltype(X)* X;
```
to
```
#define CUPS_SHIM_FUNC_DECL(X) decltype(::X)* X;
```
so that we are explicit about `decltype`ing from the globally scoped function that exists in `cups.h`

I believe that should fix the issue.