Merged revision(s) 1595213 from lucene/dev/trunk:
LUCENE-5673: MMapDirectory: Work around a "bug" in the JDK that throws a confusing OutOfMemoryError wrapped inside IOException if the FileChannel  mapping failed because of lack of virtual address space. The IOException is rethrown with more useful information about the problem, omitting the incorrect OutOfMemoryError

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1595214 13f79535-47bb-0310-9956-ffa450edef68
Merged revision(s) 1595223 from lucene/dev/trunk:
Simplify for Java 7, which has support for new IOException(message, cause)

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1595225 13f79535-47bb-0310-9956-ffa450edef68