RFR (XS) 8004713: Stackoverflowerror thrown when thread stack straddles 0x80000000

[Paul Nauman]

SPARC template interpreter uses signed comparison when checking for 
stack overflow while pushing a stack frame larger than the page size. In 
32 bit VM that can cause unnecessary StackOverflowErrors. Fix is to use 
unsigned comparison when checking for stack overflow.

http://cr.openjdk.java.net/~kvn/8004713/webrev/

Paul Nauman