some additions to axis2_defines.h

[Damitha Kumarage]

Hi,

I'll add following code into axis2_defines.h to identify calling 
conventions on different platforms

#if defined(__GNUC__)
#define AXIS2_CALL __attribute__((cdecl))
#else /* unix or win32 */
#if defined(__unix)
#define AXIS2_CALL
#else
#define AXIS2_CALL __stdcall
#endif

so that exposed functions can be declared as
void AXISCALL axis2_exposed_function()

I'll also add following

#if defined(WIN32)
#define AXIS2_STORAGE_CLASS_INFO __declspec(dllexport)
#else
#define AXIS2_STORAGE_CLASS_INFO
#endif

regards,
damitha