python3-dir.bbclass: add a separate class for Python 3

This is much cleaner than sharing python-dir.bbclass between python 2
and 3 classes, and doing confusing overrides in them.

(From OE-Core rev: 3891fcec863602a0ae6d0f3d305ea50a79a205d9)

Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/python3native.bbclass

@@ -1,6 +1,4 @@
-PYTHON_BASEVERSION = "3.5"
-
-inherit python-dir
+inherit python3-dir
 
 PYTHON="${STAGING_BINDIR_NATIVE}/${PYTHON_PN}-native/${PYTHON_PN}"
 EXTRANATIVEPATH += "${PYTHON_PN}-native"