configure: Fix for Ben's INC_osclass issue

Janet developed the fix, I documented it.

configure/CONFIG_ADDONS

@@ -376,17 +376,6 @@ USR_LIBS += $(USR_LIBS_DEFAULT)
 endif
 endif
 
-#
-#	concat specific include files
-#
-ifneq ($(strip $(INC_$(OS_CLASS))),)
-INC += $(subst -nil-,,$(INC_$(OS_CLASS)))
-else
-ifdef INC_DEFAULT
-INC+=$(INC_DEFAULT)
-endif
-endif
-
 #
 #	concat specific library contents (if defined) to SYS_PROD_LIBS
 #

documentation/RELEASE_NOTES.html

@@ -13,6 +13,20 @@
 
 <!-- Insert new items immediately below here ... -->
 
+<h3>Generating OS-specific include files</h3>
+
+<p>A fix has been applied to the build rules to permit OS-specific header files
+to be generated by adding them to the appropriate INC_&lt;osclass&gt; variable.
+To avoid problems with parallel builds, the rule to generate a header file
+should look something like this:</p>
+
+<blockquote><pre>
+$(COMMON_DIR)/os/vxWorks/file.h:
+	$(MKDIR) -p $(dir $@)
+	<i>generate-file</i> -o $(notdir $@)
+	$(MV) $(notdir $@) $@
+</pre></blockquote>
+
 <h3>Added CA->version function to CA Perl Bindings</h3>
 
 <p>This new function returns the version string from Base. The ca*.pl tools have