fix calloc() calls

* size_t nmemb (number of elements) first, then size_t size
* do not assume char is size 1 but use sizeof()
* allocate for char, not pointer to char (found by Michael McConville,
  fixes #261)

linux/LinuxProcess.c

@@ -242,7 +242,7 @@ ProcessClass LinuxProcess_class = {
 };
 
 LinuxProcess* LinuxProcess_new(Settings* settings) {
-   LinuxProcess* this = calloc(sizeof(LinuxProcess), 1);
+   LinuxProcess* this = calloc(1, sizeof(LinuxProcess));
    Object_setClass(this, Class(LinuxProcess));
    Process_init(&this->super, settings);
    return this;