Added runtime/spawn_subprocess.py. Force use posix spawn instead of fork, with API similar to subprocess. Using fork in runtime is incompatible with Xenomai, because memory is locked and this can lead to out of memory error.
/* Beremiz' header file for use by extensions */
#include "iec_types.h"
#define LOG_LEVELS 4
#define LOG_CRITICAL 0
#define LOG_WARNING 1
#define LOG_INFO 2
#define LOG_DEBUG 3
extern unsigned long long common_ticktime__;
#ifdef TARGET_LOGGING_DISABLE
#define LogMessage(level, buf, size)
#else
int LogMessage(uint8_t level, char* buf, uint32_t size);
#endif
long AtomicCompareExchange(long* atomicvar,long compared, long exchange);
