cmd/compile: change Mp{int,flt} functions into methods

Also give them more idiomatic Go names. Adding godocs is outside the
scope of this CL. (Besides, the method names almost all directly
parallel an underlying math/big.Int or math/big.Float method.)

CL prepared mechanically with sed (for rewriting mpint.go/mpfloat.go)
and gofmt (for rewriting call sites).

Passes toolstash -cmp.

Change-Id: Id76f4aee476ba740f48db33162463e7978c2083d
Reviewed-on: https://go-review.googlesource.com/20909
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
diff --git a/src/cmd/compile/internal/gc/swt.go b/src/cmd/compile/internal/gc/swt.go
index 6eca91d..81a991a 100644
--- a/src/cmd/compile/internal/gc/swt.go
+++ b/src/cmd/compile/internal/gc/swt.go
@@ -795,9 +795,9 @@
 	// sort by constant value to enable binary search
 	switch ct {
 	case CTFLT:
-		return mpcmpfltflt(n1.Val().U.(*Mpflt), n2.Val().U.(*Mpflt))
+		return n1.Val().U.(*Mpflt).Cmp(n2.Val().U.(*Mpflt))
 	case CTINT, CTRUNE:
-		return Mpcmpfixfix(n1.Val().U.(*Mpint), n2.Val().U.(*Mpint))
+		return n1.Val().U.(*Mpint).Cmp(n2.Val().U.(*Mpint))
 	case CTSTR:
 		// Sort strings by length and then by value.
 		// It is much cheaper to compare lengths than values,