Help: fix typo for CTEST_CUSTOM_TESTS_IGNORE

In commit v3.4.0-rc1~57^2 (Help: document CTEST_CUSTOM_* variables,
2015-09-17), the CTEST_CUSTOM_TESTS_IGNORE variable was documented with
a typo.

Auxiliary/vim/syntax/cmake.vim

@@ -733,7 +733,7 @@ syn keyword cmakeVariable contained
             \ CTEST_CUSTOM_POST_TEST
             \ CTEST_CUSTOM_PRE_MEMCHECK
             \ CTEST_CUSTOM_PRE_TEST
-            \ CTEST_CUSTOM_TEST_IGNORE
+            \ CTEST_CUSTOM_TESTS_IGNORE
             \ CTEST_CUSTOM_WARNING_EXCEPTION
             \ CTEST_CUSTOM_WARNING_MATCH
             \ CTEST_CVS_CHECKOUT

Help/manual/cmake-variables.7.rst

@@ -541,7 +541,7 @@ Variables for CTest
    /variable/CTEST_CUSTOM_POST_TEST
    /variable/CTEST_CUSTOM_PRE_MEMCHECK
    /variable/CTEST_CUSTOM_PRE_TEST
-   /variable/CTEST_CUSTOM_TEST_IGNORE
+   /variable/CTEST_CUSTOM_TESTS_IGNORE
    /variable/CTEST_CUSTOM_WARNING_EXCEPTION
    /variable/CTEST_CUSTOM_WARNING_MATCH
    /variable/CTEST_CVS_CHECKOUT

Help/variable/CTEST_CUSTOM_TEST_IGNORE.rst → Help/variable/CTEST_CUSTOM_TESTS_IGNORE.rst

@@ -1,5 +1,5 @@
-CTEST_CUSTOM_TEST_IGNORE
-------------------------
+CTEST_CUSTOM_TESTS_IGNORE
+-------------------------
 
 A list of regular expressions to use to exclude tests during the
 :command:`ctest_test` command.