FindMatlab: Fix typo in matlab_add_unit_test implementation

Fix typo in variable used to communicate between matlab_add_unit_test
and its helper script MatlabTestsRedirect.cmake that was introduced in
commit v3.7.0-rc1~116^2 (FindMatlab: Extend matlab_add_unit_test to run
arbitrary test code, 2016-08-30).

Modules/FindMatlab.cmake

@@ -793,7 +793,7 @@ function(matlab_add_unit_test)
             "-Dworking_directory=${${prefix}_WORKING_DIRECTORY}"
             "-DMatlab_PROGRAM=${Matlab_MAIN_PROGRAM}"
             "-Dno_unittest_framework=${${prefix}_NO_UNITTEST_FRAMEWORK}"
-            "-DMatlab_ADDITIONNAL_STARTUP_OPTIONS=${${prefix}_MATLAB_ADDITIONAL_STARTUP_OPTIONS}"
+            "-DMatlab_ADDITIONAL_STARTUP_OPTIONS=${${prefix}_MATLAB_ADDITIONAL_STARTUP_OPTIONS}"
             "-Dunittest_file_to_run=${${prefix}_UNITTEST_FILE}"
             "-Dcustom_Matlab_test_command=${${prefix}_CUSTOM_TEST_COMMAND}"
             "-Dcmd_to_run_before_test=${${prefix}_UNITTEST_PRECOMMAND}"

Modules/MatlabTestsRedirect.cmake

@@ -10,14 +10,14 @@
 #   -Dadditional_paths=""
 #   -Dno_unittest_framework=""
 #   -DMatlab_PROGRAM=matlab_exe_location
-#   -DMatlab_ADDITIONNAL_STARTUP_OPTIONS=""
+#   -DMatlab_ADDITIONAL_STARTUP_OPTIONS=""
 #   -Dtest_name=name_of_the_test
 #   -Dcustom_Matlab_test_command=""
 #   -Dcmd_to_run_before_test=""
 #   -Dunittest_file_to_run
 #   -P FindMatlab_TestsRedirect.cmake
 
-set(Matlab_UNIT_TESTS_CMD -nosplash -nodesktop -nodisplay ${Matlab_ADDITIONNAL_STARTUP_OPTIONS})
+set(Matlab_UNIT_TESTS_CMD -nosplash -nodesktop -nodisplay ${Matlab_ADDITIONAL_STARTUP_OPTIONS})
 if(WIN32)
   set(Matlab_UNIT_TESTS_CMD ${Matlab_UNIT_TESTS_CMD} -wait)
 endif()