Mac build fixes (bug 4392, r=me).

extensions/mysql/AMBuilder

@@ -8,7 +8,7 @@ compiler['CXXINCLUDES'].append(os.path.join(SM.mmsPath, 'core', 'sourcehook'))
 extension = AMBuild.AddJob('dbi.mysql.ext')
 binary = Cpp.LibraryBuilder('dbi.mysql.ext', AMBuild, extension, compiler)
 
-if AMBuild.target['platform'] == 'linux':
+if AMBuild.target['platform'] == 'linux' or AMBuild.target['platform'] == 'darwin':
 	lib = os.path.join(AMBuild.cache['MYSQL5'], 'lib', 'libmysqlclient_r.a')
 	link = [lib,
           '-lz',

extensions/mysql/mysql/MyDriver.h

@@ -39,6 +39,8 @@
 #endif
 
 #include <mysql.h>
+#include <my_global.h>
+#include <my_sys.h>
 
 #include <sh_string.h>
 #include <sh_list.h>