imaputil.imapsplit: Remove overzealous debug statement

In an IMAP run where we did not have to sync anything, I spend nearly a
fulls second in imaputil.debug() without even having debug output
enabled. imapsplit is mainly called by flagsplit() which will also do
debug output, so we get TONS of nearly duplicate debug output in the log
which makes it really hard to analyze.

Cut down the debug logging in imapsplit, we should be debug logging
stuff at a slightly higher level than here anyway.

This one-line change sped up my folder sync (without having to sync
anything) by 0.5 seconds even when debugging is disabled.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/imaputil.py

@@ -143,7 +143,6 @@ def imapsplit(imapstring):
             elif splitslen == 0:
                 # There was not even an unquoted word.
                 break
-    debug("imapsplit() returning:", retval)
     return retval
             
 flagmap = [('\\Seen', 'S'),