Fixed "u#" parser marker to pass through Unicode objects as-is without
going through the buffer interface API.
Added tests for this to the _testcapi module and updated docs.
diff --git a/Doc/ext/extending.tex b/Doc/ext/extending.tex
index 0051a02..d77a714 100644
--- a/Doc/ext/extending.tex
+++ b/Doc/ext/extending.tex
@@ -669,6 +669,8 @@
\item[\samp{u\#} (Unicode object) {[Py_UNICODE *, int]}]
This variant on \samp{u} stores into two C variables, the first one
a pointer to a Unicode data buffer, the second one its length.
+Non-Unicode objects are handled by interpreting their read buffer
+pointer as pointer to a Py_UNICODE array.
\item[\samp{es} (string, Unicode object or character buffer compatible
object) {[const char *encoding, char **buffer]}]