Clarify the preferred way of creating patch files

warnings using the --strict-warnings flag.  OpenSSL compiles on many varied

platforms: try to ensure you only use portable features.

Our preferred format for changes is "diff -u" output. One method is to use

"git diff"  Another is to generate it something like this:

Our preferred format for patch files is "git format-patch" output. For example

to provide a patch file containing the last commit in your local git repository

use the following command:

# git format-patch --stdout HEAD^ >mydiffs.patch

Another method of creating an acceptable patch file without using git is as

follows:

# cd openssl-work

# [your changes]