Fix test broken on matlab for string indicators

See Issue #231.  Maybe not completely fixed.  Not closing.

test/test_angle_brackets.m

@@ -1,16 +1,30 @@
 function s = test_angle_brackets()
 % https://savannah.gnu.org/bugs/?45084 (Fixed in Octave 4.0)
 %
-% Copyright (c) 2015-2016 Colin B. Macdonald
+% Copyright (c) 2015-2016, 2022 Colin B. Macdonald
 % SPDX-License-Identifier: BSD-3-Clause
 %
-% Fails on 3.8
+% Fails on Octave 3.8
 % >> oct38 = DOCTEST_OCTAVE && compare_versions(OCTAVE_VERSION, '4.0.0', '<');
 %
 %
-% >> s = test_angle_brackets()    % doctest: +XFAIL_IF(oct38)
+% >> disp (test_angle_brackets ())    % doctest: +XFAIL_IF(oct38)
+% I <3 U
+%
+%
+% Slightly off-topic but newer Matlab have quotes around strings.
+%
+% Here's the Octave version, without quotes:
+% >> s = test_angle_brackets()    % doctest: +SKIP_IF(oct38 || DOCTEST_MATLAB)
 % s = I <3 U
-% >> s = '<p>I heart you</p>'     % doctest: +XFAIL_IF(oct38)
+% >> s = '<p>I heart you</p>'     % doctest: +SKIP_IF(oct38 || DOCTEST_MATLAB)
 % s = <p>I heart you</p>
+%
+%
+% On Matlab, we need string indicators in the display:
+% >> s = test_angle_brackets()    % doctest: +SKIP_IF(DOCTEST_OCTAVE)
+% s = 'I <3 U'
+% >> s = '<p>I heart you</p>'     % doctest: +SKIP_IF(DOCTEST_OCTAVE)
+% s = '<p>I heart you</p>'
 
 s = 'I <3 U';