SymPyDocTestFinder: don't test functions which are not part of SymPy

these are the modules which are skipped:

array
basic
compiler.pycodegen
compiler.transformer
dense_coding_example
differential_equations
differentiation
expansion
fnmatch
functions
hydrogen
matplotlib.collections
matplotlib.colors
matplotlib.lines
matplotlib.patches
mpl_toolkits.mplot3d.axes3d
partial_differential_eqs
plotting_nice_plot
posixpath
precision
print_gtk
print_pretty
pyglet.clock
pyglet_plotting
re
series
substitution
doctest of memoization functions fix

fix doctest of functions which are decorated with one of the *_memo decorators
SymPyDocTestFinder: add additional check
minor cleanup of SymPyDocTestFinder
SymPyDocTestFinder: revert the previously added check

otherwise some methods are not doctested
Fix properties don't have a __module__ attr
doctest: Move the dependency checks to the SymPyDocTests class

The reporter prints a 's' when the dependencies for a doctest are not
met now.
always overwrite the _doctest_depends_on element of the globs dict

This fixes lots of possibly skipped doctests in e.g., ellipse.py
fix inheritance of _doctest_depends_on attr in Circle class

Set the _doctest_depends_on attr of the Circle class to an empty dict
because otherwise the inherited non empty dict of the Ellipse base class
would be used instead.
Fix issue 1947

This was harder than I initially thought but it should be fixed now.

Instead of pasting the _find_lineno function from the stdlib into the
SymPyDocTestFinder class,  I tried to fix the parts which required a modification
of _find_lineno directly in the _find function.
use descriptors to make certain attrs of baseclasses invisbile to subclasses
fix descriptor logic: recursive propagation
use the descriptor stuff in the pygletplot module

Signed-off-by: Thomas Hisch <t.hisch@gmail.com>
cleanup of the _find method in runtests.py

we don't need the regex stuff anymore. It is never executed!
debug stuff
fix _from_module is broken in py 2.5
fixed deprecation warnings in the pygletplot modules

Signed-off-by: Thomas Hisch <t.hisch@gmail.com>
Merge pull request #1969 from thisch/doctest_cleanup

Doctest cleanup
when this documentation was re-written, it was done incorrectly. this corrects that and also removes \mathrm{}
also \mapsto is more correct than \rightarrow here
don't use \mathrm{} on d in differentials in latex