develop revert source to clang-format version 11 (#293)

* OESS-98 convert plugin option to FetchContent, add tests

* Fixes for pkcfg files because of plugin option

* OESS-98 fix tools test for plugins

* Keep doxygen comments under 100 chars long - format hint

* Whitespace

* HDFFV-11144 - Reclassify CMake messages

* HDFFV-11099/11100 added help text

* Reworked switch statement to compare string instead

* Fix typo

* Update CDash mode

* Correct name of threadsafe

* Correct option name

* Undo accidental commit

* Note LLVM 10 to 11 format default changes

* Update format plugin

* Undo clang-format version 11 changes

* One more correction

tools/lib/h5diff_array.c

@@ -1279,7 +1279,7 @@ diff_datum(void *_mem1, void *_mem2, hsize_t elemtno, diff_opt_t *opts, hid_t co
                 }
                 nfound += diff_ldouble_element(mem1, mem2, elemtno, opts);
             } /*H5T_NATIVE_LDOUBLE*/
-#endif /* H5_SIZEOF_LONG_DOUBLE */
+#endif        /* H5_SIZEOF_LONG_DOUBLE */
 
             break; /* H5T_FLOAT class */