PostgreSQL INSERT ... ON CONFLICT Issue #1551

[manticore-projects]

Fixes #1551
Supports PostgreSQL INSERT ... ON CONFLICT ... DO ... according to https://www.postgresql.org/docs/current/sql-insert.html
Allow keyword KEEP, which enables another Special Oracle Test (191 are passing now)

[manticore-projects]

I have no idea, why the Maven Build fails when the Gradle Build compiles and tests fine.
The generated sources have differences (maven on left and gradle on the right):

After a bit of trial and error, I think MAVEN needs to set the following JavaCC options:
arguments = [grammar_encoding: 'UTF-8', static: 'false', java_template_type: 'modern']

(Without those, the Gradle Build also fails.)

[manticore-projects]

Very strange. The following Production would compile with the Gradle Plugin, but not with Maven:

Test myTest(): 
{
   Test result;
}
{
    (
      result=TestProduction1() { return result; }
    )
    |
    (
      result=TestProduction2() 
    ) { return result; }
}

Rewriting it solves the problem:

Test myTest(): 
{
   Test result;
}
{
    (
        (
          result=TestProduction1() { return result; }
        )
        |
        (
          result=TestProduction2() 
        )
    ) { return result; }
}