eina_cxx: Rename EAPI macro to EINA_CXX_TEST_API in Einna C++ tests

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

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/tests/eina_cxx/eina_cxx_suite.h

@@ -1,6 +1,7 @@
 #ifndef _EINA_CXX_SUITE_H
 #define _EINA_CXX_SUITE_H
 
+#ifdef __cplusplus
 #include <cassert>
 #include <algorithm>
 
@@ -18,5 +19,8 @@ void eina_test_thread(TCase* tc);
 void eina_test_optional(TCase* tc);
 void eina_test_value(TCase* tc);
 void eina_test_log(TCase* tc);
+#endif
+#define EINA_CXX_TEST_API
+#define EINA_CXX_TEST_API_WEAK
 
 #endif /* _EINA_CXX_SUITE_H */

src/tests/eina_cxx/meson.build

@@ -30,6 +30,7 @@ foreach eo_file : pub_eo_files
     command : eolian_gen + [ '-I', meson.current_source_dir(), eolian_include_directories,
                            '-o', 'h:' + join_paths(meson.current_build_dir(), eo_file + '.h'),
                            '-o', 'c:' + join_paths(meson.current_build_dir(), eo_file + '.c'),
+                           '-e', 'EINA_CXX_TEST_API',
                            '-gch', '@INPUT@'])
   priv_eo_file_target += custom_target('eolian_cxx_gen_eina_cxx_' + eo_file,
       input : eo_file,

src/tests/eina_cxx/simple.c

@@ -8,6 +8,8 @@
 
 #include <stdlib.h>
 
+#include "eina_cxx_suite.h"
+
 #include "eina_simple.eo.h"
 
 #define MY_CLASS EINA_SIMPLE_CLASS