Fix warnings about missing return values in non-void functions

These polynomial methods all returned nothing, so we can fix
the warnings by changing their return type to "void"
Change windows line ends to unix
Add const qualifier to some methods

Note that Q_poly::is_equal() was not made const -- it reduces the
polynomial, which of course modifies it. This seems odd, as it is
different from the behaviour of the two other polynomial classes. It
also seems odd to have a method name is_equal() with side effects.
Perhaps this is a bug?
Fix typo in poly_mon_mult

This was caught by a compiler warning -- the warning was previously
drowned out by the gazillion other warnings triggered in AE.cc
Convert line endings from windows to unix
Silence compiler warnings about ambiguous looking 'else'
Fix warnings about nested block comments
Fix prototype related warnings
Fix warnings about missing return values in non-void funcs
Fix warnings about comparision vs. assignment in 'if' clauses
Fix warning about unused expression result
Merge pull request #498 from fingolfin/fix-warnings

Fix warnings