Typedef most frequent types in opencl_stdint.h

pystencils/include/opencl_stdint.h

-typedef long int int64_t;
+#ifndef OPENCL_STDINT
+#define OPENCL_STDINT
+
+typedef unsigned int      uint;
+typedef unsigned int      uint_t;
+
+typedef signed char       int8_t;
+typedef signed short      int16_t;
+typedef signed int        int32_t;
+typedef signed long int   int64_t;
+typedef unsigned char     uint8_t;
+typedef unsigned short    uint16_t;
+typedef unsigned int      uint32_t;
+typedef unsigned long int uint64_t;
+
+#endif