[3.7] Add missed details of the C API introduced in 3.7. (GH-7047) (GH-7061)

* Set the limited API version for PyImport_GetModule and PyOS_*Fork
  functions.
* Add PyImport_GetModule and Py_UTF8Mode in PC/python3.def.
* Add several functions in Doc/data/refcounts.dat.
(cherry picked from commit 4e29f566e8821c09d8274eadcdd355e8b1284b8b)
diff --git a/Doc/data/refcounts.dat b/Doc/data/refcounts.dat
index f403c16..62cc938 100644
--- a/Doc/data/refcounts.dat
+++ b/Doc/data/refcounts.dat
@@ -152,6 +152,47 @@
 PyComplex_RealAsDouble:double:::
 PyComplex_RealAsDouble:PyObject*:op:0:
 
+PyContext_CheckExact:int:::
+PyContext_CheckExact:PyObject*:o:0:
+
+PyContext_ClearFreeList:int:::
+
+PyContext_Copy:PyObject*::+1:
+PyContext_Copy:PyObject*:ctx:0:
+
+PyContext_CopyCurrent:PyObject*::+1:
+
+PyContext_Enter:int:::
+PyContext_Enter:PyObject*:ctx:+1:
+
+PyContext_Exit:int:::
+PyContext_Exit:PyObject*:ctx:-1:
+
+PyContext_New:PyObject*::+1:
+
+PyContextToken_CheckExact:int:::
+PyContextToken_CheckExact:PyObject*:o:0:
+
+PyContextVar_CheckExact:int:::
+PyContextVar_CheckExact:PyObject*:o:0:
+
+PyContextVar_Get:int:::
+PyContextVar_Get:PyObject*:var:0:
+PyContextVar_Get:PyObject*:default_value:0:
+PyContextVar_Get:PyObject**:value:+1:???
+
+PyContextVar_New:PyObject*::+1:
+PyContextVar_New:const char*:name::
+PyContextVar_New:PyObject*:def:+1:
+
+PyContextVar_Set:PyObject*::+1:
+PyContextVar_Set:PyObject*:var:0:
+PyContextVar_Set:PyObject*:value:+1:
+
+PyContextVar_Reset:int:::
+PyContextVar_Reset:PyObject*:var:0:
+PyContextVar_Reset:PyObject*:token:-1:
+
 PyDate_FromDate:PyObject*::+1:
 PyDate_FromDate:int:year::
 PyDate_FromDate:int:month::
@@ -541,6 +582,9 @@
 
 PyImport_GetMagicNumber:long:::
 
+PyImport_GetModule:PyObject*::+1:
+PyImport_GetModule:PyObject*:name:0:
+
 PyImport_GetModuleDict:PyObject*::0:
 
 PyImport_Import:PyObject*::+1:
@@ -605,6 +649,9 @@
 PyInterpreterState_Delete:void:::
 PyInterpreterState_Delete:PyInterpreterState*:interp::
 
+PyInterpreterState_GetID:int64_t:::
+PyInterpreterState_GetID:PyInterpreterState*:interp::
+
 PyInterpreterState_New:PyInterpreterState*:::
 
 PyIter_Check:int:o:0:
@@ -933,6 +980,14 @@
 PyObject_AsFileDescriptor:int:::
 PyObject_AsFileDescriptor:PyObject*:o:0:
 
+PyOS_AfterFork:void:::
+
+PyOS_AfterFork_Child:void:::
+
+PyOS_AfterFork_Parent:void:::
+
+PyOS_BeforeFork:void:::
+
 PyOS_FSPath:PyObject*::+1:
 PyOS_FSPath:PyObject*:path:0:
 
@@ -1252,6 +1307,12 @@
 PySet_Size:int:::
 PySet_Size:PyObject*:anyset:0:
 
+PySlice_AdjustIndices:Py_ssize_t:::
+PySlice_AdjustIndices:Py_ssize_t:length::
+PySlice_AdjustIndices:Py_ssize_t*:start::
+PySlice_AdjustIndices:Py_ssize_t*:stop::
+PySlice_AdjustIndices:Py_ssize_t*:step::
+
 PySlice_Check:int:::
 PySlice_Check:PyObject*:ob:0:
 
@@ -1260,6 +1321,12 @@
 PySlice_New:PyObject*:stop:0:
 PySlice_New:PyObject*:step:0:
 
+PySlice_Unpack:int:::
+PySlice_Unpack:PyObject*:slice:0:
+PySlice_Unpack:Py_ssize_t*:start::
+PySlice_Unpack:Py_ssize_t*:stop::
+PySlice_Unpack:Py_ssize_t*:step::
+
 PyString_AS_STRING:const char*:::
 PyString_AS_STRING:PyObject*:string:0:
 
@@ -1410,6 +1477,15 @@
 PyTime_FromTime:int:second::
 PyTime_FromTime:int:usecond::
 
+PyTraceMalloc_Track:int:::
+PyTraceMalloc_Track:unsigned int:domain::
+PyTraceMalloc_Track:uintptr_t:ptr::
+PyTraceMalloc_Track:size_t:size::
+
+PyTraceMalloc_Untrack:int:::
+PyTraceMalloc_Untrack:unsigned int:domain::
+PyTraceMalloc_Untrack:uintptr_t:ptr::
+
 PyTuple_Check:int:::
 PyTuple_Check:PyObject*:p:0: