Better exception messages for Unicode 7 code

Unicode 7 (JDK-8032446) introduced new exceptions that can be padded out better.

Here are some examples from the changeset [1]:

+ count = bd.openings.length;
+ bd.openings = new Opening[count * 2];
+ } catch (Exception e) {
+ throw new OutOfMemoryError("Failed to allocate memory for openings");
+ }

we should print how many Opening objects were being allocated.

+ if (isBigEndian < 0 || 1 < isBigEndian ||
+ charsetFamily != CHAR_SET_ || sizeofUChar != CHAR_SIZE_) {
+ throw new IOException(HEADER_AUTHENTICATION_FAILED_);
+ }

I would like to see isBigEndian and charsetFamily values printed.

+ if (sizeofUDataInfo < 20 || headerSize < (sizeofUDataInfo + 4)) {
+ throw new IOException("Internal Error: Header size error");
+ }

Same again, why don't we print sizeofUDataInfo and headSize details in Exception ?

+ if(indexesLength<=IX_MIN_MAYBE_YES) {
+ throw new IOException("Normalizer2 data: not enough indexes");
+ }

Why don't we print indexesLength ?

Above are just a few examples. there may be some more.

[1] http://hg.openjdk.java.net/jdk9/dev/jdk/rev/86206517258d