Issue #19398: Extra slash no longer added to sys.path components in case of

empty compile-time PYTHONPATH components.  This fixes some tests in -S or -I
modes.

diff --cc Misc/NEWS
index 0d4e72da3a113b6a959e5048e930cdbf6be79b6b,cb244f3a352d5f2e1cfc33ba74bbc36e8da492e9..c463efda6170d3d68a2b0c87a5fbdeaa37995750
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -10,12 -10,9 +10,15 @@@ What's New in Python 3.7.0 alpha 
  Core and Builtins
  -----------------
  
+ - Issue #19398: Extra slash no longer added to sys.path components in case of
+   empty compile-time PYTHONPATH components.
+ 
 +- Issue #28621: Sped up converting int to float by reusing faster bits counting
 +  implementation.  Patch by Adrian Wielgosik.
 +
 +- Issue #28580: Optimize iterating split table values.
 +  Patch by Xiang Zhang.
 +
  - Issue #28583: PyDict_SetDefault didn't combine split table when needed.
    Patch by Xiang Zhang.