Moved axisnames earlier in core.jl (#132)

In order to include AxisArrays in system images we needed to move the
`axisnames` definitions earlier in the core.jl file. This appears to be an issue
with generated functions and system images. In this case, we're calling the
generated similar function which reference axisdim outside of the quote block, which
then referenced the axisnames methods defined later in the file.

Author: rofinn

Diff for: src/core.jl

@@ -222,6 +222,24 @@ HasAxes(::Type{<:AxisArray}) = HasAxes{true}()
 HasAxes(::Type{<:AbstractArray}) = HasAxes{false}()
 HasAxes(::A) where A<:AbstractArray = HasAxes(A)
 
+"""
+    axisnames(A::AxisArray)           -> (Symbol...)
+    axisnames(::Type{AxisArray{...}}) -> (Symbol...)
+    axisnames(ax::Axis...)            -> (Symbol...)
+    axisnames(::Type{Axis{...}}...)   -> (Symbol...)
+
+Returns the axis names of an AxisArray or list of Axises as a tuple of Symbols.
+"""
+axisnames(::AxisArray{T,N,D,Ax}) where {T,N,D,Ax}       = _axisnames(Ax)
+axisnames(::Type{AxisArray{T,N,D,Ax}}) where {T,N,D,Ax} = _axisnames(Ax)
+axisnames(::Type{Ax}) where {Ax<:Tuple{Vararg{Axis}}}   = _axisnames(Ax)
+@pure _axisnames(Ax) = axisnames(Ax.parameters...)
+axisnames() = ()
+@inline axisnames(::Axis{name},         B::Axis...) where {name} = tuple(name, axisnames(B...)...)
+@inline axisnames(::Type{<:Axis{name}}, B::Type...) where {name} = tuple(name, axisnames(B...)...)
+
+axisname(::Union{Type{<:Axis{name}},Axis{name}}) where {name} = name
+
 # Axis definitions
 """
     axisdim(::AxisArray, ::Axis) -> Int
@@ -449,24 +467,6 @@ function Base.summary(A::AxisArray)
 end
 
 # Custom methods specific to AxisArrays
-"""
-    axisnames(A::AxisArray)           -> (Symbol...)
-    axisnames(::Type{AxisArray{...}}) -> (Symbol...)
-    axisnames(ax::Axis...)            -> (Symbol...)
-    axisnames(::Type{Axis{...}}...)   -> (Symbol...)
-
-Returns the axis names of an AxisArray or list of Axises as a tuple of Symbols.
-"""
-axisnames(::AxisArray{T,N,D,Ax}) where {T,N,D,Ax}       = _axisnames(Ax)
-axisnames(::Type{AxisArray{T,N,D,Ax}}) where {T,N,D,Ax} = _axisnames(Ax)
-axisnames(::Type{Ax}) where {Ax<:Tuple{Vararg{Axis}}}   = _axisnames(Ax)
-@pure _axisnames(Ax) = axisnames(Ax.parameters...)
-axisnames() = ()
-@inline axisnames(::Axis{name},         B::Axis...) where {name} = tuple(name, axisnames(B...)...)
-@inline axisnames(::Type{<:Axis{name}}, B::Type...) where {name} = tuple(name, axisnames(B...)...)
-
-axisname(::Union{Type{<:Axis{name}},Axis{name}}) where {name} = name
-
 """
     axisvalues(A::AxisArray)           -> (AbstractVector...)
     axisvalues(ax::Axis...)            -> (AbstractVector...)