CMake part of replacing po4a-gettextize with po4a-updatepo

The design of po4a seems to expect it to act as a build system,
running with a config file telling it which files to build. In
version 0.68-1, the po4a-gettextize tool has changed to error out
with a comment that it's not being run the way it expects.

See https://bugs.debian.org/1020821

po4a-updatepo works for now with 0.68-1, although it prints a deprecation
message.

cmake/FindTranslationTools.cmake

@@ -17,7 +17,6 @@ This module defines the following variables:
 	DOS2UNIX_EXECUTABLE
 	PO4A-TRANSLATE_EXECUTABLE
 	PO4A-UPDATEPO_EXECUTABLE
-	PO4A-GETTEXTIZE_EXECUTABLE
 	XSLTPROC_EXECUTABLE
 
 #]=======================================================================]
@@ -83,14 +82,6 @@ set(PO4A-UPDATEPO_OPTIONS
 	-M utf-8
 )
 
-_find_translation_tool(PO4A-GETTEXTIZE_EXECUTABLE po4a-gettextize)
-set(PO4A-GETTEXTIZE_OPTIONS
-	--copyright-holder "Wesnoth Development Team"
-	-f docbook
-	-M utf-8
-	-L utf-8
-)
-
 _find_translation_tool(XSLTPROC_EXECUTABLE xsltproc)
 set(XSLTPROC_OPTIONS
 	--nonet

doc/manual/CMakeLists.txt

@@ -34,7 +34,9 @@ if(ENABLE_POT_UPDATE_TARGET)
 
 	add_custom_command(
 		OUTPUT ${PROJECT_SOURCE_DIR}/po/wesnoth-manual/wesnoth-manual.pot
-		COMMAND ${PO4A-GETTEXTIZE_EXECUTABLE} ${PO4A-GETTEXTIZE_OPTIONS}
+		COMMAND ${PO4A-UPDATEPO_EXECUTABLE} ${PO4A-UPDATEPO_OPTIONS}
+				--copyright-holder "Wesnoth Development Team"
+				-f docbook
 				-m ${CMAKE_CURRENT_SOURCE_DIR}/manual.en.xml
 				-p wesnoth-manual.pot
 		DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/manual.en.xml