[pangomm] README.win32: Update Meson build info

[Chun-wei Fan <fanchunwei src gnome org>]

commit 0c1a06bd3c6f7dc93a88a2e0f37cde67858d5d77
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Tue Jun 30 15:47:06 2020 +0800

    README.win32: Update Meson build info
    
    It is now possible to build Pango directly from a GIT checkout on Visual Studio
    builds for a while, so let people know about this.
    
    Also note that glibmm and cairomm should be built with Meson in order to use the
    Meson build files for pangomm, and that it is recommended to use the same compiler
    to build pangomm, glibmm and cairomm.

 README.win32 | 54 +++++++++++++++++++-----------------------------------
 1 file changed, 19 insertions(+), 35 deletions(-)
---
diff --git a/README.win32 b/README.win32
index eb69ed2..53f5126 100644
--- a/README.win32
+++ b/README.win32
@@ -91,46 +91,30 @@ Note that the prep-git-build target will require a working PERL installation.
 
 3.1 Meson with Visual Studio 2017 15.7.0 or later
 
-Note that currently it is not possible to build pangomm directly
-from a GIT checkout with Visual Studio using Meson.
-
 You will need to have Python 3.5.x or later installed with Meson 0.50.0
 or later in order to use this build option, in addition to glibmm,
-cairomm and libsigc++-3.x (built with Visual Studio) and PangoCairo,
-with all of their required dependencies.  The Ninja build tool is
+cairomm and libsigc++-3.x (built with Visual Studio using Meson) and
+PangoCairo, with all of their required dependencies.  The Ninja build tool is
 also required if not using --backend=[vs2017|vs2019] in the Meson
 command line, as noted towards the end of this section.
 
-Open a Visual Studio command prompt and ensure these header files can be
-found in the paths indicated by INCLUDE.  The repetitions below are
-necessary so that we reduce the likelihood that pre-C++-17 versions
-of the headers of glibmm, cairomm and libsigc++ are included, which will
-most likely not work.
-
--glibmm.h (from glibmm-2.63.x or later)
--glibmm-2.64\glibmm.h (the *same* glibmm as the previous line)
--cairomm (from cairomm-1.15.x or later)
--cairomm-1.16\cairomm.h (the *same* cairomm as the previous line)
--glibmmconfig.h (from glibmm-2.63.x or later)
--glibmm-2.64\include\glibmmconfig.h  (the *same* glibmmconfig as the previous line)
--cairommconfig.h (from cairomm-1.15.x or later)
--cairomm-1.16\include\cairommconfig.h  (the *same* cairommconfig as the previous line)
--sigc++\sigc++.h (from libsigc++-3.x or later)
--sigc++-3.0\sigc++\sigc++.h  (the *same* sigc++\sigc++.h as the previous line)
--sigc++config.h (from libsigc++-3.x or later)
--sigc++-3.0\include\sigc++config.h  (the *same* sigc++config.h as the previous line)
-
-Ensure that the import libraries of glibmm, cairomm and libsigc++-3.x
-can be found in the paths indicated by LIB.  Note that Visual Studio
-2019 can use 2017-built libraries without problems; but MSVC builds
-cannot make use of MinGW-built versions of these dependencies.  Note
-that debug builds require debug builds of these dependencies, but
-all other builds, including debugoptimized require release builds
-of these dependencies.
-
-You will need to have a working copy of PangoCairo's pkg-config files,
-which point to the corresponding locations of its headers and .lib's
-and the headers and .lib's of all of its dependencies.
+Note that for the -mm libraries (cairomm and glibmm), it is highly recommended that
+the same compiler is used to build the -mm libraries and pangomm, even if on Visual
+Studio 2017 or 2019.  One should be able to interexchange dependent C libraries that
+were built with Visual Studio 2015, 2017 or 2019 without problems
+
+Visual Studio 2019 may be able to use 2017-built -mm libraries without problems; but
+MSVC builds cannot make use of MinGW-built versions of the -mm libraries.  Note
+that 'debug' builds should only be used against dependencies that are built
+as debug builds, and 'release' and 'debugoptimized' should be only used against
+dependencies that are built as 'release' or 'debugoptimized'.  On Visual Studio
+builds in Meson, 'debugoptimized' is roughly equivilant to a Release build with
+.PDB files enabled, perhaps with some debugging features that are specific to the
+respective packages.
+
+You will need to have a working copy of glibmm, cairomm and PangoCairo's
+pkg-config files, which point to the corresponding locations of its headers
+and .lib's and the headers and .lib's of all of its dependencies.
 
 To carry out a build, do this in the same command prompt, with
 the Python interpreter, Meson executable script and Ninja executable