Add .pyo and .pyc files to the gitignore.

Apparently I used to have a global gitignore that hid these, but it
ought to be stated in the gitignore.

Test: ndk/checkbuild.py && git -C toolchain/python status
Bug: None
Change-Id: I9d6df1df8b3014c6bb278c629aab345c04abb082

.gitignore

 /Python-*/Lib/plat-win32/STDDEF.py
 /Python-*/Lib/plat-win32/regen
 /Python-*/Parser/pgen.stamp
+*.pyo
+*.pyc