Enable DDR support for Linux x86-64

[keithc-ca]

• add configure option '--enable-ddr' (enabled by default for xa64)
• enable opt_useOmrDdr accordingly
• build j9ddr.jar for inclusion in openj9.dtfj.jmod

Depends on eclipse/openj9#1399.

[keithc-ca]

The copyright failure is with a generated file: common/autoconf/generated-configure.sh.

[pshipton]

jenkins compile