make rc_sys system specific

This rearranges the configuration files so it is more clear that the
rc_sys setting is system specific.

X-Gentoo-Bug: 363957
X-Gentoo-Bug-URL: http://bugs.gentoo.org/show_bug.cgi?id=363957

etc/rc.conf.FreeBSD

@@ -1,3 +1,6 @@
+##############################################################################
+# FreeBSD SPECIFIC OPTIONS
+
 # This is the subsystem type. Valid options on FreeBSD:
 # ""        - nothing special
 # "jail"    - FreeBSD jails

etc/rc.conf.Linux

@@ -1,3 +1,6 @@
+##############################################################################
+# LINUX SPECIFIC OPTIONS
+
 # This is the subsystem type. Valid options on Linux:
 # ""        - nothing special
 # "lxc"     - Linux Containers
@@ -15,9 +18,6 @@
 # PRESENTLY in, not the virtualization the environment is capable of.
 rc_sys="@RC_SYS_DEFAULT@"
 
-##############################################################################
-# LINUX SPECIFIC OPTIONS
-
 # This is the number of tty's used in most of the rc-scripts (like
 # consolefont, numlock, etc ...)
 rc_tty_number=12

etc/rc.conf.NetBSD

@@ -1,3 +1,6 @@
+##############################################################################
+# NetBSD SPECIFIC OPTIONS
+
 # This is the subsystem type. Valid options on NetBSD:
 # ""        - nothing special
 # "prefix"  - Prefix