fix some stray untyped global variables (#523)

Author: nsajko

src/common.jl

@@ -1017,7 +1017,7 @@ end
 
 #=
 arithmetic =#
-Scalar = Union{Number, Matrix}
+const Scalar = Union{Number, Matrix}
 
 # scalar operations
 # scalar_add utilized polynomial addition. May be more performant to provide new method

src/polynomials/standard-basis/immutable-polynomial.jl

@@ -50,7 +50,7 @@ ImmutablePolynomial(1.0)
     This was modeled after [StaticUnivariatePolynomials](https://github.com/tkoolen/StaticUnivariatePolynomials.jl) by `@tkoolen`.
 
 """
-ImmutablePolynomial = ImmutableDensePolynomial{StandardBasis}
+const ImmutablePolynomial = ImmutableDensePolynomial{StandardBasis}
 export ImmutablePolynomial
 
 _typealias(::Type{P}) where {P<:ImmutablePolynomial} = "ImmutablePolynomial"

src/precompiles.jl

@@ -1,6 +1,7 @@
 # precompiles
 
-p = fromroots(Polynomial, [1,1,2])
-Multroot.multroot(p)
-gcd(p, derivative(p); method=:numerical)
-#uvw(p, derivative(p); method=:numerical)
+let p = fromroots(Polynomial, [1,1,2])
+    Multroot.multroot(p)
+    gcd(p, derivative(p); method=:numerical)
+    #uvw(p, derivative(p); method=:numerical)
+end