empty files are not treated well by headache. Better have a single line

src/plugins/instantiate/stdlib/calloc.mli

@@ -19,3 +19,5 @@
 (*  for more details (enclosed in the file licenses/LGPLv2.1).            *)
 (*                                                                        *)
 (**************************************************************************)
+
+(* register instantiation for calloc. Nothing is exported. *)

src/plugins/instantiate/stdlib/free.mli

@@ -19,3 +19,5 @@
 (*  for more details (enclosed in the file licenses/LGPLv2.1).            *)
 (*                                                                        *)
 (**************************************************************************)
+
+(* register instantiation for free. Nothing is exported. *)

src/plugins/instantiate/stdlib/malloc.mli

@@ -19,3 +19,5 @@
 (*  for more details (enclosed in the file licenses/LGPLv2.1).            *)
 (*                                                                        *)
 (**************************************************************************)
+
+(* register instantiation for malloc. Nothing is exported. *)

src/plugins/instantiate/string/memcmp.mli

@@ -19,3 +19,5 @@
 (*  for more details (enclosed in the file licenses/LGPLv2.1).            *)
 (*                                                                        *)
 (**************************************************************************)
+
+(* register instantiation for memcmp. Nothing is exported. *)

src/plugins/instantiate/string/memcpy.mli

@@ -19,3 +19,5 @@
 (*  for more details (enclosed in the file licenses/LGPLv2.1).            *)
 (*                                                                        *)
 (**************************************************************************)
+
+(* register instantiation for memcpy. Nothing is exported. *)

src/plugins/instantiate/string/memmove.mli

@@ -19,3 +19,5 @@
 (*  for more details (enclosed in the file licenses/LGPLv2.1).            *)
 (*                                                                        *)
 (**************************************************************************)
+
+(* register instantiation for memmove. Nothing is exported. *)

src/plugins/instantiate/string/memset.mli

@@ -19,3 +19,5 @@
 (*  for more details (enclosed in the file licenses/LGPLv2.1).            *)
 (*                                                                        *)
 (**************************************************************************)
+
+(* register instantiation for memset. Don't export anything *)