Fix x86 floating-point constant emission.

Previously, the basis of constant pooling was implemented, but two things were lacking:

1. The constant pools were not being emitted in the asm file.

2. A direct FP value was emitted in an FP instruction, e.g. "addss xmm0, 1.0000e00".  Curiously, at least for some FP constants, llvm-mc was accepting this syntax.

BUG= none
R=jfb@chromium.org

Review URL: https://codereview.chromium.org/291213003
diff --git a/src/IceDefs.h b/src/IceDefs.h
index 6c5cb1a..9870716 100644
--- a/src/IceDefs.h
+++ b/src/IceDefs.h
@@ -61,6 +61,7 @@
 typedef std::list<InstPhi *> PhiList;
 typedef std::vector<Variable *> VarList;
 typedef std::vector<CfgNode *> NodeList;
+typedef std::vector<Constant *> ConstantList;
 
 // SizeT is for holding small-ish limits like number of source
 // operands in an instruction.  It is used instead of size_t (which