Fix -Wsign-compare warnings in parser, scanner, regexp, runtime.

src/base/cpu.cc

Index: src/base/cpu.cc
diff --git a/src/base/cpu.cc b/src/base/cpu.cc
index 775719292065716e86ac758e26e27e7e51b36735..90ed35138319c4ee27b6ee5cab4289c03e9063c7 100644
--- a/src/base/cpu.cc
+++ b/src/base/cpu.cc
@@ -415,7 +415,7 @@ CPU::CPU()
   }
 
   // Check if CPU has non stoppable time stamp counter.
-  const int parameter_containing_non_stop_time_stamp_counter = 0x80000007;
+  const unsigned parameter_containing_non_stop_time_stamp_counter = 0x80000007;
   if (num_ext_ids >= parameter_containing_non_stop_time_stamp_counter) {
     __cpuid(cpu_info, parameter_containing_non_stop_time_stamp_counter);
     has_non_stop_time_stamp_counter_ = (cpu_info[3] & (1 << 8)) != 0;