(add-time ) overflow => not documented unexpected results

[CryptoPascal31]

Issue description

The add-time function can overflow and give unexpected results.

Steps to reproduce

Some examples:

pact> (add-time (time "2016-07-22T12:00:00Z") 10000000000000000000000000000000000)
"-157918-10-27T19:13:49Z" 

pact> (add-time (time "2016-07-22T12:00:00Z") 1000000000000000000000000000000000000000000000000000000000000000000000000)
"2016-07-22T12:00:00Z"

As you can see in some cases:

• The time wraps around
• The function doesn't work at all and returns the original time.

Expected Behavior

Either:

• The function should trigger a transaction failure when an overflow is expected.
• In the documentation, flag the add-time as "unsafe" without prior boundaries check.

[rsoeldner]

@CryptoPascal31 thank you, we will look into it