Add windows build instructions

Makefile.am

@@ -2,9 +2,14 @@ ACLOCAL_AMFLAGS = -I m4
 
 SUBDIRS = src headers
 
-EXTRA_DIST = makefile.vc nmake.opt \
-	README.md CREDITS \
-  doc/DATASTORES.md doc/g_serialized.txt
+EXTRA_DIST = \
+  CREDITS \
+  doc/BUILDING-ON-WINDOWS.md \
+  doc/DATASTORES.md \
+  doc/g_serialized.txt \
+  makefile.vc \
+  nmake.opt \
+	README.md
 
 AUTOMAKE_OPTIONS = dist-zip foreign
 

README.md

@@ -36,11 +36,11 @@ Using Autotools:
     ${srcdir}/configure # in build dir
     make # build
     make check # test
-    make install # install
+    make install # or install-strip
 
 ### Microsoft Windows
 
-TODO
+See doc/BUILDING-ON-WINDOWS.md
 
 ## Using
 

doc/BUILDING-ON-WINDOWS.md

@@ -0,0 +1,46 @@
+Building on Windows
+===================
+
+On Windows systems you can choose between two different compilers:
+- MinGW / MSYS
+  This represents a smart porting of a minimalistic Linux-like
+  development toolkit
+- Microsoft Visual Studio .NET (aka MSVC)
+  This is the standard platform development toolkit from Microsoft.
+
+# Using MinGW / MSYS
+
+We assume that you have already installed the MinGW compiler and the
+MSYS shell.
+Building 'librttopo' under Windows is then more or less like building
+on any other UNIX-like system. If you have unpacked the sources as
+C:\librttpopo-<version>, then the required steps are:
+
+  cd c:/librttopo-<version>
+  export "CFLAGS=-I/usr/local/include"
+  export "LDFLAGS=-L/usr/local/lib"
+  ./configure
+  make
+  make install
+  # or (in order to save some disk space)
+  make install-strip
+
+
+# Using Microsoft Visual Studio .NET
+
+We assume that you have already installed Visual Studio enabling the
+command
+line tools. Note that you are expected to the Visual Studio command
+prompt shell
+rather than the GUI build environment. If you have unpacked the
+sources as
+C:\librttpopo-<version>, then the required steps are:
+
+  cd c:\librttopo-<version>
+  nmake /f makefile.vc
+  nmake /f makefile.vc install
+
+Please note: the MSVC build configuration is based on the OSGeo4W
+distribution. Any depending library (e.g. GEOS) is expected to be
+already installed on C:\OSGeo4W
+