This missed PyErr_NoMemory() could cause a SystemError when calling
_symtable.symtable().
(cherry picked from commit ad65f15581173542f1d2a9968a63bee272510ce3)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>

(cherry picked from commit fc439d20de32b0ebccca79a96e31f83b85ec4eaf)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>

When comprehensions switched to using a nested scope, the old
code for generating a temporary name to hold the accumulation
target became redundant, but was never actually removed.

Patch by Nitish Chandra.
(cherry picked from commit 3a087beddd9f0955eb9080a6fd1499ff89ca74bf)

Co-authored-by: Nitish Chandra <nitishchandrachinta@gmail.com>

The current behaviour of yield expressions inside comprehensions  and
generator expressions is essentially an accident of implementation - it
arises implicitly from the way the compiler handles yield expressions inside
nested functions and generators.

Since the current behaviour wasn't deliberately designed, and is inherently
confusing, we're deprecating it, with no current plans to reintroduce it.
Instead, our advice will be to use a named nested generator definition
for cases where this behaviour is desired.

Lexically first global and nonlocal syntax errors at given scope should be detected first.

* group the (stateful) runtime globals into various topical structs
* consolidate the topical structs under a single top-level _PyRuntimeState struct
* add a check-c-globals.py script that helps identify runtime globals

Other globals are excluded (see globals.txt and check-c-globals.py).

The latter function is more readable, faster and doesn't raise exceptions.

The latter function is more readable, faster and doesn't raise exceptions.