Fix compilation error

g++ -g  -I./include/ -c word.cpp
In file included from ./include/impress.h:3:0,
                 from word.cpp:29:
./include/stat.h: In function ‘std::istream& operator>>(std::istream&, Random&)’:
./include/stat.h:165:36: error: ‘LONG_MAX’ was not declared in this scope
./include/stat.h: In constructor ‘Random::Random(long int)’:
./include/stat.h:180:7: error: ‘LONG_MAX’ was not declared in this scope
./include/stat.h: In member function ‘void Random::reset(long int)’:
./include/stat.h:228:7: error: ‘LONG_MAX’ was not declared in this scope

Signed-off-by: David Sterba <dsterba@suse.cz>