DOC: additional notes about FFTs, typo fixes, etc.
MAINT: Use boolean defaults for boolean parameter overwrite_x
MAINT: Use boolean defaults for boolean overwrite_x parameter
DOC: Add simple ifft Returns section
DOC: Add examples for DCT, minor changes to DCT docstrings
DOC: elaborate on rfft and dct efficiencies
Merge pull request #2775 from endolith/patch-3

DOC: fftpack: add more notes about FFTs, real FFTs, fix typos, change boolean defaults to False