Replaced the text in reference/extension_types.rst by links to the corresponding sections in the userguide.

Transfered a note from the reference guide extension types to the userguide.

Also reject conflicting duplicates of top-level directives.
Closes #2230.

Support more C file extensions when searching modules during coverage analysis: .cc and .cxx in addition to the current .c and .cpp.
Closes #2266.

Avoid segfault due to a bug in g++ 4.4.7 when the -Os setting for the module init function is enabled.
Closes #2235.

Replace text with links

Transfered type casting

Further optimise int/float comparison

Repair and simplify unrolled PyLong comparison loop that used PyLong_BASE incorrectly (it's an exponential base, not a factor).

Fix incrementally increasing indentation level in utility functions due to repeated opening braces inside of C preprocessor conditionals.

Speed up 1-argument method calls, especially those to CyFunctions, by avoiding the creation of a bound method object.

Transfered keyword only arguments.

Transfer optional arguments