Fix typo and gcc-7 warnings (#401)

* Fix typo in hf mf csave help
* Fix gcc 7 warning: '~' on an expression of type bool [-Wbool-operation], use logical ! not instead of ~
* Fix gcc 7 warning: ‘memset’ used with length equal to number of elements without multiplication by element size [-Wmemset-elt-size]
* Fix gcc 7 warning: warning: duplicate ‘const’ declaration specifier [-Wduplicate-decl-specifier]