Rework zlib patching

Break CMake changes, rc mod and zlib prefixing out into separate
patches.  To make the diff more useful, incorporate file moves into the
patching process so we can diff the current zlib.h and our zlib.h.in (as
well as the same thing for zconf) rather than deleting and adding.

zlib/CMakeLists.txt

@@ -19,7 +19,11 @@ if (ENABLE_ZLIB)
   ExternalProject_Add(ZLIB_BLD
     URL "${CMAKE_CURRENT_SOURCE_DIR}/zlib"
     BUILD_ALWAYS ${EXT_BUILD_ALWAYS} ${LOG_OPTS}
-    PATCH_COMMAND ${PATCH_EXECUTABLE};-E;-p1;${PATCH_OPTIONS};-i;${CMAKE_CURRENT_SOURCE_DIR}/zlib.patch
+    PATCH_COMMAND ${PATCH_EXECUTABLE};-E;-p1;${PATCH_OPTIONS};-i;${CMAKE_CURRENT_SOURCE_DIR}/zlib_cmake.patch
+    COMMAND ${CMAKE_COMMAND};-E;rename;<SOURCE_DIR>/zlib.h;<SOURCE_DIR>/zlib.h.in
+    COMMAND ${CMAKE_COMMAND};-E;rename;<SOURCE_DIR>/zconf.h;<SOURCE_DIR>/zconf.h.in
+    COMMAND ${PATCH_EXECUTABLE};-E;-p1;${PATCH_OPTIONS};-i;${CMAKE_CURRENT_SOURCE_DIR}/zlib_rc.patch
+    COMMAND ${PATCH_EXECUTABLE};-E;-p1;${PATCH_OPTIONS};-i;${CMAKE_CURRENT_SOURCE_DIR}/zlib_prefix.patch
     CMAKE_ARGS
     ${BUILD_TYPE_SPECIFIER}
     -DZ_PREFIX_STR=${Z_PREFIX_STR}