zzz.R does not parse Oracle java version

[GerardTromp]

Had a problem with the java version check in Oracle java.

1. Oracle java has versions such as 11.0.2 etc.
   The existing pattern match expects only a single digit in the major (11) part, and fails to load the Namespace completely.

Fixing the pattern match to allow more than one digit, allow loading of the Namespace with the warning about version.

Seems that the check should a) determine oracle vs open-jdk and have patterns that are appropriate to each.

[lgatto]

Hi @GerardTromp - I have

$ java -version 
openjdk version "12.0.2" 2019-07-16
OpenJDK Runtime Environment (build 12.0.2+10)
OpenJDK 64-Bit Server VM (build 12.0.2+10, mixed mode)

which works when installing from Github. What is your version string?