This reverts commit d49062fd.

When detecting an invalid system configuration for overflow checks, at least print a warning, instead of leaving a dangling live exception behind.

This fixes Github issue #2819.

Document trashcan

@cython.trashcan directive to enable the Python trashcan for deallocations

Optimise internal fallback method call to ".__await__()" in Py3.7+ by directly unpacking the method instance.

Closes #2850.

Fix early binding example.
Closes GH-2848.

Closes #1470.

Closes GH-2845.

GCC diagnostic pragmas were introduced in GCC 4.6, so augment the GCC
compiler check with a version check to avoid compilation errors with GCC
< 4.6.

Avoid GCC diagnostic pragma if GCC < 4.6

GCC diagnostic pragmas were introduced in GCC 4.6, so augment the GCC
compiler check with a version check to avoid compilation errors with GCC
< 4.6.

REF: make Utils dependency-free by moving search_include_directories