plugin compile errors

In file included from SDK/plugin.h:8:0,
                 from plugin.cpp:1:
SDK/plugincommon.h:41:4: error: #error "You must define one of WIN32, LINUX or FREEBSD"
   #error "You must define one of WIN32, LINUX or FREEBSD"
    ^
In file included from SDK/plugin.h:9:0,
                 from plugin.cpp:1:
SDK/amx/amx.h:185:47: warning: ‘packed’ attribute ignored for field of type ‘char [20]’ [-Wattributes]
   #define PACKED        __attribute__((packed))
                                               ^
SDK/amx/amx.h:215:25: note: in expansion of macro ‘PACKED’
   char name[sEXPMAX+1]  PACKED;
                         ^
SDK/amx/amx.h:185:47: warning: ‘packed’ attribute ignored for field of type ‘char’ [-Wattributes]
   #define PACKED        __attribute__((packed))
                                               ^
SDK/amx/amx.h:265:25: note: in expansion of macro ‘PACKED’
   char    file_version  PACKED; /* file format version */
                         ^
SDK/amx/amx.h:185:47: warning: ‘packed’ attribute ignored for field of type ‘char’ [-Wattributes]
   #define PACKED        __attribute__((packed))
                                               ^
SDK/amx/amx.h:266:25: note: in expansion of macro ‘PACKED’
   char    amx_version   PACKED; /* required version of the AMX */
                         ^
SDK/amx/amx.h:384:72: error: ‘size_t’ has not been declared
 int AMXAPI amx_GetString(char *dest,const cell *source, int use_wchar, size_t size);
                                                                        ^
SDK/amx/amx.h:404:83: error: ‘size_t’ has not been declared
 int AMXAPI amx_SetString(cell *dest, const char *source, int pack, int use_wchar, size_t size);
                                                                                   ^
plugin.cpp:9:1: error: ‘PLUGIN_EXPORT’ does not name a type
 PLUGIN_EXPORT bool PLUGIN_CALL Load(void **ppData)
 ^
plugin.cpp:16:1: error: ‘PLUGIN_EXPORT’ does not name a type
 PLUGIN_EXPORT void PLUGIN_CALL Unload()
 ^
plugin.cpp: In function ‘cell YourNativeNameHere(AMX*, cell*)’:
plugin.cpp:22:52: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings]
         logprintf("I haz made my first plugin!! :)");
                                                    ^
plugin.cpp: At global scope:
plugin.cpp:32:1: error: ‘PLUGIN_EXPORT’ does not name a type
 PLUGIN_EXPORT unsigned int PLUGIN_CALL Supports()
 ^
plugin.cpp:37:1: error: ‘PLUGIN_EXPORT’ does not name a type
 PLUGIN_EXPORT int PLUGIN_CALL AmxLoad(AMX *amx)
 ^
plugin.cpp:42:1: error: ‘PLUGIN_EXPORT’ does not name a type
 PLUGIN_EXPORT int PLUGIN_CALL AmxUnload(AMX *amx)
 ^