Add test programs to github.

tests/hellothreads3/hellothreads3.cpp

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+#include <string.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <unistd.h>
+
+// Global variable:
+int iA = 2;
+int iB = 5;
+
+void barA (int v) {
+    printf("barA: %i\n", v);
+    sleep(20);
+    printf("barA: %i\n", v);
+}
+
+void barB (int v) {
+    printf("barB: %i\n", v);
+    sleep(20);
+    printf("barB: %i\n", v);
+}
+
+
+void* fooA (void* p) {
+    // Print value received as argument:
+    printf("fooA: Value recevied as argument in starting routine: ");
+    printf("%i\n", *(int*)p);
+
+    barA(*(int*)p);
+
+    // Return reference to global variable:
+    pthread_exit(&iA);
+}
+
+void* fooB (void* p) {
+    // Print value received as argument:
+    printf("fooB: Value recevied as argument in starting routine: ");
+    printf("%i\n", *(int*)p);
+
+    barB(*(int*)p);
+
+    // Return reference to global variable:
+    pthread_exit(&iB);
+}
+
+int main (void) {
+    // Declare variable for thread's ID:
+    pthread_t idA;
+    pthread_t idB;
+
+    int jA = 1;
+    int jB = 4;
+
+    pthread_create(&idA, NULL, fooA, &jA);
+    pthread_create(&idB, NULL, fooB, &jB);
+
+    int* ptrA;
+    int* ptrB;
+
+    // Wait for fooA() and retrieve value in ptr;
+    pthread_join(idA, (void**)&ptrA);
+
+    // Wait for fooB() and retrieve value in ptr;
+    pthread_join(idB, (void**)&ptrB);
+
+    printf("Value recevied by parent from child: ");
+    printf("%i\n", *ptrA);
+
+    printf("Value recevied by parent from child: ");
+    printf("%i\n", *ptrB);
+
+    return 0;
+}
+