libc/stdio: Provide proper TAP output for fmemopen/open_[w]memstream.

A *.t file should provide Test Anything Protocol output so that it can be
run using the Perl "prove" tool.

tools/regression/lib/libc/stdio/test-fmemopen.t

@@ -7,4 +7,9 @@ executable=`basename $0 .t`
 
 make $executable 2>&1 > /dev/null
 
-exec ./$executable
+echo 1..1
+if ./$executable; then
+	echo ok 1 - $executable successful
+else
+	echo not ok 1 - $executable failed
+fi

tools/regression/lib/libc/stdio/test-open_memstream.t

@@ -7,4 +7,9 @@ executable=`basename $0 .t`
 
 make $executable 2>&1 > /dev/null
 
-exec ./$executable
+echo 1..1
+if ./$executable; then
+	echo ok 1 - $executable successful
+else
+	echo not ok 1 - $executable failed
+fi

tools/regression/lib/libc/stdio/test-open_wmemstream.t

@@ -7,4 +7,9 @@ executable=`basename $0 .t`
 
 make $executable 2>&1 > /dev/null
 
-exec ./$executable
+echo 1..1
+if ./$executable; then
+	echo ok 1 - $executable successful
+else
+	echo not ok 1 - $executable failed
+fi