Install modules in a subdir to fit with platform name mangling

Take advantage of fix_platform_name's new tricks in test '122 shared
module'

test cases/common/122 shared module/installed_files.txt

@@ -1,3 +1,3 @@
-usr/lib/libnosyms.so
-?gcc:usr/lib/libnosyms?implib
-?msvc:usr/lib/libnosyms.pdb
+usr/lib/modules/libnosyms?so
+?gcc:usr/lib/modules/libnosyms?implib
+?msvc:usr/lib/modules/nosyms.pdb

test cases/common/122 shared module/meson.build

@@ -13,8 +13,6 @@ e = executable('prog', 'prog.c',
 test('import test', e, args : m)
 
 # Shared module that does not export any symbols
-shared_module('nosyms', 'nosyms.c', install : true,
-              # Because we don't have cross-platform library support in
-              # installed_files.txt
-              name_suffix : 'so',
-              name_prefix : 'lib')
+shared_module('nosyms', 'nosyms.c',
+  install : true,
+  install_dir : join_paths(get_option('libdir'), 'modules'))

test cases/windows/7 dll versioning/installed_files.txt

@@ -14,9 +14,9 @@
 ?msvc:usr/libexec/customdir.dll
 ?msvc:usr/libexec/customdir.lib
 ?msvc:usr/libexec/customdir.pdb
-?msvc:usr/lib/module.dll
-?msvc:usr/lib/module.lib
-?msvc:usr/lib/module.pdb
+?msvc:usr/lib/modules/module.dll
+?msvc:usr/lib/modules/module.lib
+?msvc:usr/lib/modules/module.pdb
 ?gcc:usr/bin/?libsome-0.dll
 ?gcc:usr/lib/libsome.dll.a
 ?gcc:usr/bin/?libnoversion.dll
@@ -27,5 +27,5 @@
 ?gcc:usr/lib/libonlysoversion.dll.a
 ?gcc:usr/libexec/?libcustomdir.dll
 ?gcc:usr/libexec/libcustomdir.dll.a
-?gcc:usr/lib/?libmodule.dll
-?gcc:usr/lib/libmodule.dll.a
+?gcc:usr/lib/modules/?libmodule.dll
+?gcc:usr/lib/modules/libmodule.dll.a

test cases/windows/7 dll versioning/meson.build

@@ -49,4 +49,6 @@ shared_library('customdir', 'lib.c',
   install : true,
   install_dir : get_option('libexecdir'))
 
-shared_module('module', 'lib.c', install : true)
+shared_module('module', 'lib.c',
+  install : true,
+  install_dir: join_paths(get_option('libdir'), 'modules'))