Add atkeyword macro to basedocs.jl, move some docs inline.

base/dft.jl

@@ -374,6 +374,32 @@ end
 
 # FFTW module (may move to an external package at some point):
 if Base.USE_GPL_LIBS
+
+    @doc """
+        fft(A [, dims])
+
+    Performs a multidimensional FFT of the array `A`. The optional `dims` argument specifies an
+    iterable subset of dimensions (e.g. an integer, range, tuple, or array) to transform along.
+    Most efficient if the size of `A` along the transformed dimensions is a product of small
+    primes; see `nextprod()`. See also `plan_fft()` for even greater efficiency.
+
+    A one-dimensional FFT computes the one-dimensional discrete Fourier transform (DFT) as
+    defined by
+
+    ```math
+    \\operatorname{DFT}(A)[k] =
+      \\sum_{n=1}^{\\operatorname{length}(A)}
+      \\exp\\left(-i\\frac{2\\pi
+      (n-1)(k-1)}{\\operatorname{length}(A)} \\right) A[n].
+    ```
+
+    A multidimensional FFT simply performs this operation along each transformed dimension of `A`.
+
+    Higher performance is usually possible with multi-threading. Use `FFTW.set_num_threads(np)`
+    to use `np` threads, if you have `np` processors.
+    """ ->
+    fft
+
     include("fft/FFTW.jl")
     importall .FFTW
     export FFTW, dct, idct, dct!, idct!, plan_dct, plan_idct, plan_dct!, plan_idct!