[JVM] Fix references to unsupported Java versions

README.pod

@@ -35,7 +35,7 @@ github by visiting http://github.com/perl6/nqp/tree/master and clicking
 
 NQP can run on three different backends: MoarVM, the JVM, and JavaScript.
 The JVM and JavaScript backends are currently experimental.  The JVM backend
-requires JDK 1.9 (Also known as JDK 9)
+requires JDK 1.9 (also known as JDK 9) or higher.
 
 Decide on which backends you want it to run, and configure and build it as
 follows:

docs/release_guide.pod

@@ -39,10 +39,10 @@ Resolve any problems that may still exist. Issues that impact backends
 other than MoarVM may potentially be ignored for a release for now.
 Check on the IRC channel if you have any questions.
 
-You will need JVM installed for the jvm tests to run. On Debian, you
-can install it with:
+You will need a JDK (Java Development Kit) installed for building and
+running tests for the jvm backend. On Debian, you can install it with:
 
-    sudo apt-get install openjdk-7-jdk openjdk-7-jre
+    sudo apt-get install openjdk-11-jdk
 
 =item 4.
 

tools/lib/NQP/Config/NQP.pm

@@ -218,7 +218,7 @@ sub configure_jvm_backend {
         print "got: $_";
         if (/(?:java|jdk) version "(\d+)(?:\.(\d+))?/) {
             $jvm_found = 1;
-            if ( $1 > 1 || $1 == 1 && $2 >= 8 ) {
+            if ( $1 > 1 || $1 == 1 && $2 >= 9 ) {
                 $ijvm->{ok} = $jvm_ok = 1;
             }
             $got = $_;
@@ -230,7 +230,7 @@ sub configure_jvm_backend {
         push @errors, "No JVM (java executable) in path; cannot continue";
     }
     elsif ( !$jvm_ok ) {
-        push @errors, "Need at least JVM 1.8 (got $got)";
+        push @errors, "Need at least JVM 1.9 (got $got)";
     }
     $self->sorry(@errors) if @errors;