procutil: move assignments closer to reassignments

Doing reassignments is an anti-pattern IMHO, but I see how it makes sense here.
When first looking at this code after jumping here with ctags, I missed the
fact that stdout was reassigned. To make the code clearer, the assignments
should be as close as possible to the reassignments.

mercurial/utils/procutil.py

@@ -37,10 +37,6 b' from ..utils import resourceutil'
 
 osutil = policy.importmod('osutil')
 
-stderr = pycompat.stderr
-stdin = pycompat.stdin
-stdout = pycompat.stdout
-
 
 def isatty(fp):
     try:
@@ -79,6 +75,10 b' def make_line_buffered(stream):'
     return LineBufferedWrapper(stream)
 
 
+stderr = pycompat.stderr
+stdin = pycompat.stdin
+stdout = pycompat.stdout
+
 # glibc determines buffering on first write to stdout - if we replace a TTY
 # destined stdout with a pipe destined stdout (e.g. pager), we want line
 # buffering (or unbuffered, on Windows)