fix for more warnings.

- modifier code was using sizeof() without knowing the sizeof the array when clearing the modifier type array.
- use BLI_snprintf rather then sprintf where the size of the string is known.
- particle drawing code kept a reference to stack float values (not a problem at the moment but would crash if accessed later).

source/blender/python/generic/mathutils_matrix.c

@@ -879,9 +879,6 @@ static char Matrix_invert_doc[] =
 "\n"
 "   Set the matrix to its inverse.\n"
 "\n"
-"   :return: an instance of itself.\n"
-"   :rtype: :class:`Matrix`\n"
-"\n"
 "   .. note:: :exc:`ValueError` exception is raised.\n"
 "\n"
 "   .. seealso:: <http://en.wikipedia.org/wiki/Inverse_matrix>\n"