PPC: [regexp] correctly advance zero length matches for global/unicode.

Port  57d202d8

R=yangguo@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=v8:2952
LOG=N

Review URL: https://codereview.chromium.org/1646613002

Cr-Commit-Position: refs/heads/master@{#33566}

src/regexp/ppc/regexp-macro-assembler-ppc.cc

@@ -851,8 +851,11 @@ Handle<HeapObject> RegExpMacroAssemblerPPC::GetCode(Handle<String> source) {
           __ cmpi(current_input_offset(), Operand::Zero());
           __ beq(&exit_label_);
           // Advance current position after a zero-length match.
+          Label advance;
+          __ bind(&advance);
           __ addi(current_input_offset(), current_input_offset(),
                   Operand((mode_ == UC16) ? 2 : 1));
+          if (global_unicode()) CheckNotInSurrogatePair(0, &advance);
         }
 
         __ b(&load_char_start_regexp);