Fix interfacing with and remaking dynamic objects on MS-Windows.

 load.c (load_object, load_file): Accept an additional argument
 DLP and return in it a pointer that can be used to unload the
 dynamic object.
 read.c (eval): Call load_file with an additional argument, and
 record the pointer returned there in the 'struct file' object of
 dynamic objects in that object's 'struct file'.
 commands.c (execute_file_commands): Unload dynamic objects
 before remaking them, to avoid failure to remake if the OS doesn't
 allow overwriting objects that are in use.
 filedef.h (struct file): New member dlopen_ptr.
 gnumake.h (GMK_EXPORT): Define to dllexport/dllimport
 decorations for Windows and to nothing on other platforms.
 (gmk_eval, gmk_expand, gmk_add_function): Add GMK_EXPORT qualifier
 to prototypes.
 makeint.h (MAIN): Define before including gnumake.h, to give
 correct dllexport decorations to exported functions.
 (load_file): Adjust prototype.
 loadapi.c: Don't include gnumake.h, since makeint.h already
 includes it, and takes care of defining MAIN before doing so.
 build_w32.bat (LinkGCC): Produce an import library for functions
 exported by Make for loadable dynamic objects.

 w32/compat/posixfcn.c (dlclose): New function.
 w32/include/dlfcn.h (dlclose): Add prototype.

 scripts/features/load: Fix signatures of testload_gmk_setup and
 explicit_setup, to bring them in line with the documentation.

2 files changed, 12 insertions, 0 deletions

diff --git a/w32/compat/posixfcn.c b/w32/compat/posixfcn.c
index cafc864..0a08c65 100644
--- a/w32/compat/posixfcn.c
+++ b/w32/compat/posixfcn.c
@@ -338,6 +338,17 @@ dlsym (void *handle, const char *name)
   return (void *)addr;
 }
 
+int
+dlclose (void *handle)
+{
+  if (!handle || handle == INVALID_HANDLE_VALUE)
+    return -1;
+  if (!FreeLibrary (handle))
+    return -1;
+
+  return 0;
+}
+
 
 #endif	/* MAKE_LOAD */
 
diff --git a/w32/include/dlfcn.h b/w32/include/dlfcn.h
index c95fee2..c8523ad 100644
--- a/w32/include/dlfcn.h
+++ b/w32/include/dlfcn.h
@@ -9,5 +9,6 @@
 extern void *dlopen (const char *, int);
 extern void *dlsym (void *, const char *);
 extern char *dlerror (void);
+extern int   dlclose (void *);
 
 #endif	/* DLFCN_H */