Add entry for unittest documentation.

Doc/Makefile.deps

@@ -57,6 +57,7 @@ LIBFILES= $(MANSTYLES) $(COMMONTEX) \
 	lib/libinspect.tex \
 	lib/libdifflib.tex \
 	lib/libdoctest.tex \
+	lib/libunittest.tex \
 	lib/libtypes.tex \
 	lib/libtraceback.tex \
 	lib/libpickle.tex \

Doc/lib/lib.tex

@@ -112,6 +112,7 @@ and how to embed it in other applications.
 
 \input{libmisc}                 % Miscellaneous Services
 \input{libdoctest}
+\input{libunittest}
 \input{libmath}
 \input{libcmath}
 \input{librandom}