Conform to PP 4-16 to 4-19 in http://www.sco.com/developers/devspecs/mipsabi.pdf.

Fix to allow Bit 15 overflow.

Change-Id: I9ff679ffba3b6139d929291e6d857d03d57cece4
diff --git a/include/impl/ELFObject.hxx b/include/impl/ELFObject.hxx
index 1aa2b38..5212733 100644
--- a/include/impl/ELFObject.hxx
+++ b/include/impl/ELFObject.hxx
@@ -379,7 +379,7 @@
 
     case R_MIPS_HI16:
       A = A & 0xFFFF;
-      *inst |= (((S + A + 0xFFFF8000) >> 16) & 0xFFFF);
+      *inst |= (((S + A + 0x8000) >> 16) & 0xFFFF);
       break;
 
     case R_MIPS_LO16: