Fix type of `Long.MIN_VALUE` and `Long.MAX_VALUE` #3100

Long.MIN_VALUE and Long.MAX_VALUE should be of type long like it is in the JDK sources.

This change shouldn't impact any previously working proofs since these values get translated to the correct numbers in JavaDL as sort int regardless.

Theoretically this change could introduce new type issues when parsing previously working Java code, but this seems unlikely since the int types would probably have been widened to long before anyway.