detect mod and rem by 0

src/main/scala/leon/purescala/PrettyPrinter.scala

src/main/scala/leon/verification/DefaultTactic.scala

src/main/scala/leon/verification/InjectAsserts.scala

src/main/scala/leon/verification/VerificationCondition.scala

...ion/verification/purescala/invalid/BVDivisionByZero.scala

...on/verification/purescala/invalid/BVRemainderByZero.scala

...ssion/verification/purescala/invalid/DivisionByZero.scala

...ression/verification/purescala/invalid/ModuloByZero.scala

...sion/verification/purescala/invalid/RemainderByZero.scala

...ssion/verification/purescala/valid/BVDivisionByZero.scala

...sion/verification/purescala/valid/BVDivisionByZero2.scala

...ression/verification/purescala/valid/DivisionByZero.scala