re PR go/51874 (Many libgo testsuite failures on IRIX)

	PR go/51874
math: Don't use libc log2 and trunc functions.

From-SVN: r184300

libgo/go/math/floor.go

@@ -58,11 +58,8 @@ func ceil(x float64) float64 {
 //	Trunc(±Inf) = ±Inf
 //	Trunc(NaN) = NaN
 
-//extern trunc
-func libc_trunc(float64) float64
-
 func Trunc(x float64) float64 {
-	return libc_trunc(x)
+	return trunc(x)
 }
 
 func trunc(x float64) float64 {

libgo/go/math/log10.go

@@ -21,11 +21,8 @@ func log10(x float64) float64 {
 // Log2 returns the binary logarithm of x.
 // The special cases are the same as for Log.
 
-//extern log2
-func libc_log2(float64) float64
-
 func Log2(x float64) float64 {
-	return libc_log2(x)
+	return log2(x)
 }
 
 func log2(x float64) float64 {