DOC: make curve_fit nomenclature same as leastsq

The curve_fit help used N for the number of data points and M for the number of parameters, but lasts which has these reversed. Fixes issue #3172
Merge pull request #3187 from alchemyst/master

DOC: make curve_fit nomenclature same as leastsq
DOC: linalg: typo ("withouth")
Merge pull request #3199 from larsmans/typos

DOC: linalg: typo ("withouth")
DOC: typos
DOC optional -> optimal
DOC optional -> optimal
typos throughout the codebase
TST: special: account for floating point limitations in cos-integral test
Merge pull request #3200 from argriffing/moretypos

MAINT: fix typos
MAINT: add benchmark mode to runtests.py
Merge pull request #3204 from pv/mpmath-test-fix

TST: special: account for floating point limitations in cos-integral test
Merge pull request #3205 from pv/runbench

MAINT: add benchmark mode to runtests.py
BUG: sparse/sparsetools: catch c++ exceptions

These can appear e.g. in out-of-memory situations or from other causes
inside STL.
MAINT: sparse: Tweak the definition of test_throw_error to avoid multiple instantations.
GEN: sparse: regenerate sparsetools
Merge pull request #3215 from pv/swig-badalloc

 BUG: sparse/sparsetools: catch c++ exceptions
ENH: add axis keyword to dendrogram function

This fixes gh-1325 (Trac #798). It allows scipy dendrograms to easily be
plotted on custom axes, e.g. as part of a larger figure. It does not import
pylab at all if an axis is provided, which is useful for those who are using
the matplotlib API.
MAINT: changed 'axis' to 'ax' throughout dendrogram code.

Also changed "axis_gca" flag to be more descriptive "trigger_redraw".
TST: added test for dendrogram plotting

Tests plotting to pylab.gca() and to an axis passed in as an argument.