Make cmdline_param work and conform to rc.d layout

- Rename cmdline_param to kernel_cmdline
- Move to /etc/rc.d/functions.d where it belongs

configs/syslinux-iso/overlay/etc/archiso/functions

-# vim: set ft=sh:
-
-cmdline_param ()
-{
-    for param in ${CMDLINE}; do
-        case "${param}" in
-            $1=*) echo "${param##*=}"; return ;;
-            *) continue ;;
-        esac
-    done
-    [ -n "${2}" ] && echo "${2}"
-}

configs/syslinux-iso/overlay/etc/rc.d/archiso

 # vim: set ft=sh:
 . /etc/rc.conf
 . /etc/rc.d/functions
-. /etc/archiso/functions
 
 
 scan_network ()

configs/syslinux-iso/overlay/etc/rc.d/functions.d/archiso

+# vim: set ft=sh:
+
+# kernel_cmdline <param>
+# Looks for a parameter on the kernel's boot-time command line.
+#
+# returns: 0 if param was found. Also prints its value if it was a K=V param.
+#          1 if it was not
+#
+kernel_cmdline ()
+{
+    for param in $(/bin/cat /proc/cmdline); do
+        case "${param}" in
+            $1=*) echo "${param##*=}"; return 0 ;;
+            $1) return 0 ;;
+            *) continue ;;
+        esac
+    done
+
+    return 1
+}