Merge branch 'bc/csprng-mktemps'

Pick a better random number generator and use it when we prepare
temporary filenames.

* bc/csprng-mktemps:
  wrapper: use a CSPRNG to generate random file names
  wrapper: add a helper to generate numbers from a CSPRNG

diff --cc Makefile
Simple merge

diff --cc compat/winansi.c
Simple merge

diff --cc config.mak.uname
Simple merge

diff --cc git-compat-util.h
Simple merge