Drop confusing splash cmdline and --enable-progress configure option

This patch reverts back to the progress/status behavior of Finit < v3.0
because this is what most users expect, including the maintainer.  The
resulting code and configure script is a lot simpler to understand and
maintain:

- No more --enable-progress or --enable-progress-classic configure
  flags.  Instead a progress_style variable in helpers.c that can
  be changed at compile time for those that really need it.
- No more 'splash' kernel commnand line option.  This turned out to
  be *very* confusing to many users who believed it was some sort of
  graphical splash screen à la Plymouth.

Also, when Finit debug is enabled we now have a global 'debug' flag
which now alo controls if klogctl() should be called to prevent the
kernel logs to the console or not.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

doc/cmdline.md

@@ -2,12 +2,11 @@ Tips & Tricks with the kernel cmdline
 =====================================
 
 This document summarizes the different boot parameters that can be
-passed on the Linux kernel command line.  Not just limited to Finit.
+passed on the Linux kernel command line.  Not limited to Finit.
 
-* `debug`, or `--debug`  
-    Enable debug mode.  The former syntax also enable kernel debug, and
-    the latter only in Finit.  Debug messages are printed to the console
-    until a syslog daemon has been started.
+* `debug`__
+    Enable kernel debug.  Debug messages are printed to the console
+    until Finit starts up, the syslog daemon then empties `/dev/kmsg`
 
 * `init=/bin/sh`  
     Bypass system default init and tell kernel to start a shell.  Note,
@@ -32,7 +31,4 @@ passed on the Linux kernel command line.  Not just limited to Finit.
     so a `tty [1] @console nologin` configuration presents you with a
     root console without login.
 
-* `splash`  
-    Display Finit splash screen with progress at bootstrap and shutdown.
-
 For more on kernel boot paramaters, see the man page `bootparam(7)`.