Add an operation that checks whether we are at the start of the string.

src/regexp-macro-assembler-ia32.cc

Index: src/regexp-macro-assembler-ia32.cc
===================================================================
--- src/regexp-macro-assembler-ia32.cc	(revision 864)
+++ src/regexp-macro-assembler-ia32.cc	(working copy)
@@ -162,6 +162,11 @@
 }
 
 
+void RegExpMacroAssemblerIA32::CheckNotAtStart(Label* on_not_at_start) {
+  UNIMPLEMENTED();
+}
+
+
 void RegExpMacroAssemblerIA32::CheckCharacterLT(uc16 limit, Label* on_less) {
   __ cmp(edx, limit);
   BranchOrBacktrack(less, on_less);