Add support for a CONFIG_SITE.local file

.gitignore

@@ -6,6 +6,7 @@
 /html/
 /include/
 /templates/
+/configure/*.local
 O.*/
 /QtC-*
 *.orig

configure/CONFIG_SITE

@@ -175,3 +175,5 @@ GCC_PIPE = NO
 #  run at build-time, e.g. set the LD_LIBRARY_PATH environment variable.
 LINKER_USE_RPATH = YES
 
+# Overrides for the settings above may appear in a CONFIG_SITE.local file
+-include $(CONFIG)/CONFIG_SITE.local

documentation/RELEASE_NOTES.html

@@ -16,6 +16,15 @@
 
 <!-- Insert new items immediately below here ... -->
 
+<h3>Support for CONFIG_SITE.local in Base</h3>
+
+<p>This feature is mostly meant for use by developers; configuration
+settings that would normally appear in Base/configure/CONFIG_SITE can now
+be put in a locally created base/configure/CONFIG_SITE.local file instead
+of having go modify or replace the original. A new .gitignore pattern
+tells git to ignore all configure/*.local files.</p>
+
+
 <h2 align="center">Changes from the 3.14 branch since 3.15.5</h2>
 
 <!-- Insert inherited items immediately below here ... -->