move sstrdup, scalloc, smalloc, srealloc to libi3, improve error messages

include/libi3.h

@@ -14,4 +14,32 @@
  */
 char *socket_path_from_x11();
 
+/**
+ * Safe-wrapper around malloc which exits if malloc returns NULL (meaning that
+ * there is no more memory available)
+ *
+ */
+void *smalloc(size_t size);
+
+/**
+ * Safe-wrapper around calloc which exits if malloc returns NULL (meaning that
+ * there is no more memory available)
+ *
+ */
+void *scalloc(size_t size);
+
+/**
+ * Safe-wrapper around realloc which exits if realloc returns NULL (meaning
+ * that there is no more memory available).
+ *
+ */
+void *srealloc(void *ptr, size_t size);
+
+/**
+ * Safe-wrapper around strdup which exits if malloc returns NULL (meaning that
+ * there is no more memory available)
+ *
+ */
+char *sstrdup(const char *str);
+
 #endif