added a test for "-g" option.
added verbose option "-v".  changed the switch to enable "guess mode" "-g" to "-G".
updated test for "-G" option.
define file_index.db as a constant.
added wrapper scripts.
updated Makefile
added "lazy mode" which assumed index of header files are always the
same as far as in the same project. This is not always true but almost
always true. This option is enabled by specifying "-l" option.
Merge branch 'devel' of https://github.com/katonori/cxxtags into devel