This adds basic support for parsing USDT arguments having
operands in the powerpc64 format. The following operand
formats are supported for now:
  * iNUM or i-NUM
  * REG or %rREG
  * NUM(REG) or -NUM(REG) or NUM(%rREG) or -NUM(%rREG)
  * REG,REG or %rREG,%rREG

Where NUM represents a numeric constant and REG represents
a general-purpose register.
Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>