BR2_HAVE_DOCUMENTATION: add option to remove documentation from target

Some packages' install-strip target install quite big documentation,
so create an option to remove it similar to the existing man/info options.

Config.in

@@ -348,6 +348,13 @@ config BR2_HAVE_INFOPAGES
 	  If you say n here, your target will not contain any
 	  infopage.
 
+config BR2_HAVE_DOCUMENTATION
+	bool "documentation on the target"
+	help
+	  Leave the documentation on the target.
+	  If you say n here, your target will not contain any
+	  documentation.
+
 config BR2_HAVE_DEVFILES
 	bool "development files in target filesystem"
 	help

package/Makefile.autotools.in

@@ -256,6 +256,9 @@ $(PROJECT_BUILD_DIR)/autotools-stamps/%_target_installed:
 	$(if $(BR2_HAVE_INFOPAGES),,for d in info share/info; do \
 		rm -rf $(TARGET_DIR)/$$d $(TARGET_DIR)/usr/$$d; \
 	done)
+	$(if $(BR2_HAVE_DOCUMENTATION),,for d in doc share/doc; do \
+		rm -rf $(TARGET_DIR)/$$d $(TARGET_DIR)/usr/$$d; \
+	done)
 	$(Q)mkdir -p $(@D)
 	touch $@