maint: make spacing around "=" consistent, even in IF_LINT

maint: make spacing around "=" consistent, even in IF_LINT

E.g.,
  -  size_t desired_width IF_LINT (= 0);
  +  size_t desired_width IF_LINT ( = 0);
Use this command:
  g grep -l IF_LINT | grep '\.[ch]$' \
    | xargs perl -pi -e 's/(IF_LINT \()= /$1 = /'