fix github issue #38 - indentation vs `if {}'

fix github issue #38 - indentation vs `if {}'

Fixes #38

In 3.6.1, some code in mfind0(detect.c) was mis-indented in a way
which suggested that the grouping within braces might not be what was
intended, and that was right--there was a pair of braces missing when
compared with older versions of the code involved.  A previous patch
(post-#38) had changed the indentation to match the surrounding braces
without really addressing the issue.  But it turned out not to make
any difference either way since mundetected is only used by hiders
and eels.  This reorganizes the relevant code to make it simpler to
understand, I hope.