fixed up the makefile a little

- allow for user specified compiler
- allow for users CXXFLAGS + LDFLAGS
- removed unnecessary implicit .o rule
- changed CC to CXX (c++ instead of c)

Signed-off-by: Steven Honeyman <stevenhoneyman@users.noreply.github.com>
fixed a warning (int->long int)

Signed-off-by: Steven Honeyman <stevenhoneyman@users.noreply.github.com>
fixed an ambiguous operator precedence warning

Signed-off-by: Steven Honeyman <stevenhoneyman@users.noreply.github.com>