flac.md: Example as "level 4" heading

Added an example as "level 4" heading at the end of the apodization functions. 
 - The example is meant as a suggestion to the text, but 
 - The "level 4" heading is meant as a test.

Author: H2Swine

man/flac.md

@@ -854,6 +854,24 @@ parameter (defaulting to 5e-1) is applied for the smallest used window:
 For example, subdivide_tukey(2/5e-1) results in the same taper as that of
 tukey(25e-2) and subdivide_tukey(5) in the same taper as of tukey(1e-1). 
 
+#### example (for illustration - impractically long!):
+`-A "flattop;gauss(1e-1);tukey(3e-2);punchout_tukey(3/-9e-4/54e-2);subdivide_tukey(5/7e-1);hannning`  
+The encoder will for each subframe try all the following in order, 
+estimate the size, and pick the best which is then used to encode:
+- First taper the subframe with the flattop function;  
+- Start anew at a gauss (STDEV of ten percent of the subframe);  
+- Start anew at a tukey window that tapers 15% of each end (total 30%);  
+- Then each of 3 windows generated by punchout_tukey: each generated by 
+	deleting ("punching out") a third of the subframe, with a small 
+	negative overlap, tapering off 27% off each end (total 54e-2);  
+- Finally a sequence of windows produced by subdivide_tukey: like the 
+	two previous ones, it applies cosine-tapering, but steeper tapers 
+	at the ends (the base case tapers 7e-1 divided by 5 i.e. 14 percent 
+	of the subframe), and successively trying subdivisions: the first 
+	and last half of the subframe, then the first/middle/last third etc, 
+	up to generating five windows, one for each fifth of the subframe.  
+- Wrong and discarded: "hanning" (a not-uncommon mixup of "hamming" and "hann").
+
 
 # SEE ALSO