Support --help option

include/esidl.h : Add the declaration for help()
src/driver.cpp (main) : Support --help option
src/help.cpp (help) : Show help in help2man style
Makefile.am (esidl_SOURCES) : Add src/help.cpp
Generate the man page of esidl

configure.ac : Check help2man
Makefile.am (man1_MANS) : Add esidl.1 which is generated by help2man
esidl.spec.in (%files) : Add %{_mandir}/man1/esidl.1.gz
esidl.spec.in (BuildRequires) : Add help2man
debian/control (Build-Depends) : Add help2man