port: fix: correct safe integer range for bitwise ops

[He-Pin]

refs: google/jsonnet#1217
google/jsonnet@499b0db
refs: google/jsonnet#1240

golden google/jsonnet#1217

[stephenamar-db]

oh yeah, it's on my personal todo list. our number bound checks are bad and we need to do a thorough refactoring.

[He-Pin]

@stephenamar-db Do you plan to add this to the 0.5.0 release? :)

[stephenamar-db]

unlikely.