Add √ as synonym for sqrt

Author: jiahao

base/exports.jl

@@ -440,6 +440,7 @@ export
     unsigned,
     widemul,
     zero,
+    √,
 
 # specfun
     airy,

base/math.jl

@@ -16,7 +16,7 @@ export sin, cos, tan, sinh, cosh, tanh, asin, acos, atan,
        besselj0, besselj1, besselj, bessely0, bessely1, bessely,
        hankelh1, hankelh2, besseli, besselk, besselh,
        beta, lbeta, eta, zeta, polygamma, invdigamma, digamma, trigamma,
-       erfinv, erfcinv
+       erfinv, erfcinv, √
 
 import Base: log, exp, sin, cos, tan, sinh, cosh, tanh, asin,
              acos, atan, asinh, acosh, atanh, sqrt, log2, log10,
@@ -279,6 +279,7 @@ sqrt(x::Float64) = box(Float64,sqrt_llvm(unbox(Float64,x)))
 sqrt(x::Float32) = box(Float32,sqrt_llvm(unbox(Float32,x)))
 sqrt(x::Real) = sqrt(float(x))
 @vectorize_1arg Number sqrt
+const √=sqrt
 
 for f in (:ceil, :trunc, :significand) # :rint, :nearbyint
     @eval begin