Add 1.5.3-otp-18, 1.5.3-otp-19

[dbernheisel]

This adds

• 1.5.3-otp-18
• 1.5.3-otp-19

1.5.3-otp-20 seems to already exist, but is tagged as 1.5.3

These use the hex.pm Bob-built versions since the precompiled artifacts on GitHub for these OTP versions don't exist.

[c0b]

wonder does 1.5 still really have many users? could you talk more about your use cases; Don't you have any upgrade plans in the following 12 months

https://github.com/elixir-lang/elixir/blob/master/lib/elixir/pages/Compatibility%20and%20Deprecations.md#compatibility-and-deprecations

Our original plan in this repo is to remove some old versions every year; these are on the list I would like to remove in this year of 2019

• 1.5.3, 1.5
• 1.5.3-slim, 1.5-slim
• 1.5.3-alpine, 1.5-alpine
• 1.4.5, 1.4
• 1.4.5-slim, 1.4-slim

[dbernheisel]

yes I do plan on upgrading soon but thought it may be helpful for others. I'll be happy to close.

I wrote these as a test to ensure that the 1.5.3 tag was actually running with OTP 20 (it is), and to compare the difference to these other older OTP versions. Since I wrote it, I figured I'd contribute it.

[c0b]

I'd like to keep this open for some more days, to see if how others comment; may be useful to others, we never know