fix compilation on Julia 0.7

Author: mlubin

src/NaNMath.jl

@@ -1,11 +1,13 @@
 __precompile__()
 module NaNMath
 
+const libm = Base.libm_name
+
 for f in (:sin, :cos, :tan, :asin, :acos, :acosh, :atanh, :log, :log2, :log10,
           :lgamma, :log1p)
     @eval begin
-        ($f)(x::Float64) = ccall(($(string(f)),Base.Math.libm), Float64, (Float64,), x)
-        ($f)(x::Float32) = ccall(($(string(f,"f")),Base.Math.libm), Float32, (Float32,), x)
+        ($f)(x::Float64) = ccall(($(string(f)),libm), Float64, (Float64,), x)
+        ($f)(x::Float32) = ccall(($(string(f,"f")),libm), Float32, (Float32,), x)
         ($f)(x::Real) = ($f)(float(x))
         function ($f)(x::AbstractArray{T}) where T<:Number
             Base.depwarn("$f{T<:Number}(x::AbstractArray{T}) is deprecated, use $f.(x) instead.", $f)
@@ -19,8 +21,8 @@ end
 sqrt(x::Real) = x < 0.0 ? NaN : Base.sqrt(x)
 
 # Don't override built-in ^ operator
-pow(x::Float64, y::Float64) = ccall((:pow,Base.Math.libm),  Float64, (Float64,Float64), x, y)
-pow(x::Float32, y::Float32) = ccall((:powf,Base.Math.libm), Float32, (Float32,Float32), x, y)
+pow(x::Float64, y::Float64) = ccall((:pow,libm),  Float64, (Float64,Float64), x, y)
+pow(x::Float32, y::Float32) = ccall((:powf,libm), Float32, (Float32,Float32), x, y)
 pow(x::Number,y::Number) = pow(float(x),float(y))
 
 """