Issue #1971 - Part 2: Update ICU source to 63.2.

intl/icu/source/tools/genren/README

@@ -9,13 +9,26 @@ It also does not currently work well in an out-of-source situation.
 The following instructions are for Linux version.
 - urename.h file should be generated after implementation is complete for a release.
 - the version number for a release should be set according to the list in source/common/unicode/uvernum.h
-- In this [genren] directory, run 
 
-    "make install-header"
+Before generating urename.h, the layout engine header files must be installed from the harfbuzz project.
+This is prerequisite for the icu layoutex (Paragraph Layout) project, which is subject to renaming.
+(Using the svn command is the simplest way of getting just the files from one subdirectory of the git project.)
+
+    cd icu4c/source
+    svn export https://github.com/behdad/icu-le-hb/trunk/src layout
+
+- Regenerate urename.h
+
+    cd icu4c/source/tools/genren
+    make install-header
 
 - urename.h will be updated in icu/source/common/unicode/urename.h  **in your original source directory**
+- Warnings concerning bad namespace (not 'icu') on UCaseMap can be ignored.
 - Eyeball the new file for errors
 
+    cd icu4c/source
+    svn diff common/unicode/urename.h
+
 - Other make targets here
 
     clean      - cleans out intermediate files