Integrate MSW, OS X and iOS build instructions into doxygen

Make build instructions available in doxygen but keep the old
folder structure.

docs/doxygen/Doxyfile

@@ -100,7 +100,7 @@ ALIASES += appearance_brief{2}="\htmlonly<div class="appearance_brief"><table><t
 ALIASES += genericAppearance_brief{2}="\htmlonly<div class="appearance_brief"><table><tr><td>\endhtmlonly\n\1\htmlonly</td><td>\endhtmlonly\n\image html generic/\2.png\n\htmlonly</td></tr></table></div>\endhtmlonly"
 
 # aliases for the creation of "named member groups"
-# USAGE: the first argument must not contain spaces and be a unique identifier 
+# USAGE: the first argument must not contain spaces and be a unique identifier
 #        of the member group for the class being documented;
 #        the second argument is the member group name and can contain spaces
 #        See wxString as an usage example.
@@ -292,6 +292,9 @@ WARN_LOGFILE           = doxygen.log
 INPUT                  = mainpages \
                          groups \
                          overviews \
+                         ../ios \
+                         ../msw \
+                         ../osx \
                          ../../interface
 INPUT_ENCODING         = UTF-8
 FILE_PATTERNS          = *.h *.md

docs/doxygen/mainpages/platdetails.h

@@ -62,8 +62,7 @@ distribution.
 wxOSX/Cocoa is the port of wxWidgets for the OS X platform. It requires
 OS X 10.7 or later and fully supports 64 bit builds.
 
-For further information, please see the files in @c docs/osx in the
-distribution.
+@subpage plat_osx_install "Build and Install Instructions"
 
 
 
@@ -105,7 +104,7 @@ This port can be compiled with several compilers including Microsoft Studio
 VC++ 2003 or later, Borland 5.5, MinGW32, Cygwin as well as cross-compilation
 with a Linux-hosted MinGW32 tool chain.
 
-For further information, please see the files in docs/msw in the distribution.
+@subpage plat_msw_install "Build and Install Instructions"
 
 @subsection page_port_wxmsw_resources Resources and Application Icon
 
@@ -175,7 +174,7 @@ wxiOS is a port of wxWidgets using Cocoa touch libraries for iOS. It is very
 basic in it current form, but is included for further improvements and very
 simple applications. It requires iOS 9 or later and fully supports 64 bit builds.
 
-For further information, please see the files in docs/ios in the distribution.
+@subpage plat_ios_install "Build Instructions"
 
 @section page_port_nativedocs Native Toolkit Documentation