Rename option to --detect-shared-borders and add a test

man/tippecanoe.1

@@ -148,6 +148,8 @@ which may not be what you want.
 \-ap or \-\-drop\-polygons: Let "dot" dropping at lower zooms apply to polygons too
 .IP \(bu 2
 \-ag or \-\-calculate\-feature\-density: Add a new attribute, \fB\fCtippecanoe_feature_density\fR, to each feature, to record how densely features are spaced in that area of the tile. You can use this attribute in the style to produce a glowing effect where points are densely packed. It can range from 0 in the sparsest areas to 255 in the densest.
+.IP \(bu 2
+\-ab or \-\-detect\-shared\-borders: In the manner of TopoJSON \[la]https://github.com/mbostock/topojson/wiki/Introduction\[ra], detect borders that are shared between multiple polygons and simplify them identically in each polygon. This takes more time and memory than considering each polygon individually.
 .RE
 .SS Doing less
 .RS
@@ -289,14 +291,14 @@ If a tile is larger than 500K, it will try encoding that tile at progressively
 lower resolutions before failing if it still doesn't fit.
 .SH Development
 .PP
-Requires sqlite3 (should already be installed on MacOS). Rebuilding the manpage
+Requires sqlite3 and zlib (should already be installed on MacOS). Rebuilding the manpage
 uses md2man (\fB\fCgem install md2man\fR).
 .PP
 Linux:
 .PP
 .RS
 .nf
-sudo apt\-get install libsqlite3\-dev
+sudo apt\-get install libsqlite3\-dev zlib1g\-dev
 .fi
 .RE
 .PP