Bump for 9.1.6.0

[Truffle] Assume that Graal is automatically set up if RUBY_BIN is set.

Update for 9.1.5.0 release

Properly replace packed 2-tuple entries with those coming in.

Fixes jruby#4124.

Update version for 9.1.3.0 release

Bump version to 1.7.26

Merge branch 'master' into truffle-head

# Conflicts:
#	ci.hocon
#	truffle/src/main/java/org/jruby/truffle/language/DataNode.java

[Truffle] Do not use the build pack on truffle-head as it won't conta…

…in the latest truffle.