Rename libmsl to libsystem

libsystem/init/.gitignore

@@ -0,0 +1 @@
+*.o

libsystem/init/__premain.c

@@ -0,0 +1,27 @@
+#include <liballoc.h>
+#include <stdint.h>
+#include <system.h>
+
+extern volatile uint8_t __bss_start[];
+extern volatile uint8_t __bss_end[];
+
+extern void app_main (void);
+
+static void clear_bss (void) {
+  uint8_t* p = (uint8_t*)__bss_start;
+  while (p < __bss_end) {
+    *p++ = 0;
+  }
+}
+
+void __premain (void) {
+  clear_bss ();
+
+  liballoc_init ();
+
+  app_main ();
+
+  liballoc_deinit ();
+
+  quit ();
+}

libsystem/init/src.mk

@@ -0,0 +1,3 @@
+c += init/__premain.c
+
+o += init/__premain.o