Normalize comments in *nix build system m4 files

Normalization include:
- Use dnl for everything that can be ommitted when configure is built in
  favor of the shell comment character # which is visible in the output.
- Line length normalized to 80 columns
- Dots for most of the one line sentences
- Macro definitions include similar pattern header comments now

config.m4

@@ -1,5 +1,3 @@
-dnl config.m4 for extension recode
-
 PHP_ARG_WITH([recode],
   [for recode support],
   [AS_HELP_STRING([[--with-recode[=DIR]]],

config9.m4

@@ -1,5 +1,3 @@
-dnl config.m4 for extension recode
-
 dnl Check for extensions with which Recode can not work
 if test "$PHP_RECODE" != "no"; then
   test "$PHP_IMAP"  != "no" && recode_conflict="$recode_conflict imap"