Add spec for gen_server:terminate/6,7

This is to prevent dialyzer warning "no local return".
asn1: Fix EXTERNAL (1994 variant) type conversion

Missed to add seqtag handling for EXTERNAL type conversion,
bug introduced in c266196c016fc1156c7a18cfeec4920ee4075519
Merge branch 'dgud/asn1/fix-seqtag/OTP-12326' into maint

* dgud/asn1/fix-seqtag/OTP-12326:
  asn1: Fix EXTERNAL (1994 variant) type conversion
Merge branch 'siri/gen_server/try-catch/OTP-12263' into maint

* siri/gen_server/try-catch/OTP-12263:
  Add spec for gen_server:terminate/6,7