Rename fake-msi.c to makemsi.c.

It's now a sensible source flie containing a set of routines that do
something coherently connected to each other, so it doesn't deserve
that 'fake-' prefix that I used for the previous monolithic files full
of tangled-together stuff.

While I'm here, I've also made up nicer (i.e. more distinguishable)
random magic numbers for the structure-type disambiguation.

Makefile.am

@@ -7,7 +7,7 @@ lib_LTLIBRARIES = libwinterop.so.la libmsi.so.la libpreload.la
 libwinterop_so_la_SOURCES = fake-winterop.c makecab.c memory.c		\
 memory.h dupstr.c dupstr.h subproc.c subproc.h uchars.c uchars.h
 
-libmsi_so_la_SOURCES = fake-msi.c md5.c memory.c memory.h version.c	\
+libmsi_so_la_SOURCES = makemsi.c md5.c memory.c memory.h version.c	\
 dupstr.c dupstr.h subproc.c subproc.h uchars.c uchars.h
 
 libpreload_la_SOURCES = preload.c

makemsi.c

@@ -1,15 +1,13 @@
 #include <assert.h>
 #include <stdio.h>
-#include <stdlib.h>
 #include <stdint.h>
-#include <stdbool.h>
-#include <stdarg.h>
 #include <string.h>
+#include <limits.h>
 #include <uchar.h>
+
 #include <err.h>
 
 #include <fcntl.h>
-#include <sys/mman.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ -19,8 +17,18 @@
 #include "subproc.h"
 #include "uchars.h"
 
+/*
+ * The same routine MsiCloseHandle is used by our client to dispose of
+ * three kinds of structure that _we_ think of as completely different
+ * types. So we must ensure all three start with distinct magic number
+ * fields, so as to know what kind we're being asked to close.
+ */
 typedef struct MsiTypePrefix {
-    enum { MAIN, VIEW, RECORD } type;
+    enum {
+        MAIN = 0x2B7FB8B8,
+        VIEW = 0x1570B0E3,
+        RECORD = 0x62365065
+    } type;
 } MsiTypePrefix;
 
 typedef struct MsiMainCtx {