edje_cxx: Edje.hh depends on already set EAPI, explicitly define

Patch from a series of patches to rename EAPI symbols to specific
library DSOs.

So we can remove EAPI from other libraries, we need to make this
library non-dependent on this symbol being already defined.

EAPI was designed to be able to pass
```__attribute__ ((visibility ("default")))``` for symbols with
GCC, which would mean that even if -fvisibility=hidden was used
when compiling the library, the needed symbols would get exported.

MSVC __almost__ works like GCC (or mingw) in which you can
declare everything as export and it will just work (slower, but
it will work). But there's a caveat: global variables will not
work the same way for MSVC, but works for mingw and GCC.

For global variables (as opposed to functions), MSVC requires
correct DSO visibility for MSVC: instead of declaring a symbol as
export for everything, you need to declare it as import when
importing from another DSO and export when defining it locally.

With current EAPI definitions, we get the following example
working in mingw and MSVC (observe it doesn't define any global
variables as exported symbols).

Example 1:
dll1:
```
EAPI void foo(void);

EAPI void bar()
{
  foo();
}
```
dll2:
```
EAPI void foo()
{
  printf ("foo\n");
}
```

This works fine with API defined as __declspec(dllexport) in both
cases and for gcc defining as
```__atttribute__((visibility("default")))```.

However, the following:
Example 2:

dll1:

```
EAPI extern int foo;
EAPI void foobar(void);

EAPI void bar()
{
  foo = 5;
  foobar();
}
```

dll2:

```
EAPI int foo = 0;
EAPI void foobar()
{
  printf ("foo %d\n", foo);
}
```

This will work on mingw but will not work for MSVC. And that's why
EAPI is the only solution that worked for MSVC.

Co-authored-by: João Paulo Taylor Ienczak Zanette <jpaulotiz@gmail.com>
Co-authored-by: Ricardo Campos <ricardo.campos@expertise.dev>
Co-authored-by: Lucas Cavalcante de Sousa <lucks.sousa@gmail.com>

src/lib/edje/Edje.hh

@@ -3,6 +3,36 @@
 
 #ifdef EFL_BETA_API_SUPPORT
 
+#ifdef EAPI
+# undef EAPI
+#endif
+
+#ifdef _WIN32
+# ifdef EFL_BUILD
+#  ifdef DLL_EXPORT
+#   define EAPI __declspec(dllexport)
+#  else
+#   define EAPI
+#  endif
+# else
+#  define EAPI __declspec(dllimport)
+# endif
+# define EAPI_WEAK
+#else
+# ifdef __GNUC__
+#  if __GNUC__ >= 4
+#   define EAPI __attribute__ ((visibility("default")))
+#   define EAPI_WEAK __attribute__ ((weak))
+#  else
+#   define EAPI
+#   define EAPI_WEAK
+#  endif
+# else
+#  define EAPI
+#  define EAPI_WEAK
+# endif
+#endif
+
 #include <Edje.eo.hh>
 
 #endif