Add some extra stub modules.

Also for use in test programs: stub modules that provide non-
functional versions of logging, printing and storage.

stubs/no-storage.c

@@ -0,0 +1,40 @@
+/*
+ * Stub module implementing the saved-session storage APIs for tools
+ * that don't load or save sessions.
+ */
+
+#include "putty.h"
+
+settings_w *open_settings_w(const char *sessionname, char **errmsg)
+{ return NULL; }
+void write_setting_s(settings_w *handle, const char *key, const char *value)
+{ unreachable("where did you get a settings_w from?"); }
+void write_setting_i(settings_w *handle, const char *key, int value)
+{ unreachable("where did you get a settings_w from?"); }
+void write_setting_fontspec(settings_w *handle, const char *name, FontSpec *fs)
+{ unreachable("where did you get a settings_w from?"); }
+void write_setting_filename(settings_w *handle, const char *name, Filename *fn)
+{ unreachable("where did you get a settings_w from?"); }
+void close_settings_w(settings_w *handle)
+{ unreachable("where did you get a settings_w from?"); }
+
+settings_r *open_settings_r(const char *sessionname)
+{ return NULL; }
+char *read_setting_s(settings_r *handle, const char *key)
+{ return NULL; }
+int read_setting_i(settings_r *handle, const char *key, int defvalue)
+{ return defvalue; }
+FontSpec *read_setting_fontspec(settings_r *handle, const char *name)
+{ return fontspec_new_default(); }
+Filename *read_setting_filename(settings_r *handle, const char *name)
+{ return filename_from_str(""); }
+void close_settings_r(settings_r *handle) { }
+
+void del_settings(const char *sessionname) {}
+
+settings_e *enum_settings_start(void)
+{ return NULL; }
+bool enum_settings_next(settings_e *handle, strbuf *out)
+{ unreachable("where did you get a settings_e from?"); }
+void enum_settings_finish(settings_e *handle)
+{ unreachable("where did you get a settings_e from?"); }