[vectorIntrinsics] Post merge cleanup for x86 code gen

[Viswanathan, Sandhya]

Please find below a webrev which does post merge cleanup for vectorIntrinsics:
http://cr.openjdk.java.net/~sviswanathan/vectorIntrinsics/MergeCleanUp/webrev.00/

The post merge clean-up mainly involves the following:
- Extending the usage of emit_int16 and emit_int24 in the assembler to new instructions.
- Removal of BasicType from reduction methods.

Best Regards,
Sandhya