Merge 3.4's PCbuild/readme.txt update.
All the new information in 3.4's readme.txt was already here, but the
wrong name was used to refer to the script. Also reworded the sentence.
diff --git a/PCbuild/readme.txt b/PCbuild/readme.txt
index 26739a3..26622f5 100644
--- a/PCbuild/readme.txt
+++ b/PCbuild/readme.txt
@@ -208,8 +208,9 @@
to be somewhere on your PATH. More recent versions of OpenSSL may
need a later version of NASM. If OpenSSL's self tests don't pass,
you should first try to update NASM and do a full rebuild of
- OpenSSL. get_externals.py also downloads a snapshot of NASM, and the
- libeay and ssleay sub-projects use that version of nasm.exe.
+ OpenSSL. If you use the PCbuild\get_externals.bat method
+ for getting sources, it also downloads a version of NASM which the
+ libeay/ssleay sub-projects use.
The libeay/ssleay sub-projects expect your OpenSSL sources to have
already been configured and be ready to build. If you get your sources