cmake, meson: Change library filename to libxml2.so.16.0.0

We have to follow Autotools here.

Fixes #882.

CMakeLists.txt

@@ -410,6 +410,7 @@ endif()
 
 set(LIBXML_MINOR_COMPAT 14)
 math(EXPR LIBXML_SOVERSION "${LIBXML_MAJOR_VERSION} + ${LIBXML_MINOR_COMPAT}")
+math(EXPR LIBXML_AGE "${LIBXML_MINOR_VERSION} - ${LIBXML_MINOR_COMPAT}")
 set_target_properties(
     LibXml2
     PROPERTIES
@@ -417,7 +418,7 @@ set_target_properties(
     OUTPUT_NAME xml2
     POSITION_INDEPENDENT_CODE ON
     PREFIX lib
-    VERSION ${PROJECT_VERSION}
+    VERSION "${LIBXML_SOVERSION}.${LIBXML_AGE}.${LIBXML_MICRO_VERSION}"
     SOVERSION ${LIBXML_SOVERSION}
 )
 

meson.build

@@ -478,6 +478,8 @@ foreach file : xml_opt_src
 endforeach
 
 v_min_compat = 14
+so_version = v_maj + v_min_compat
+age = v_min - v_min_compat
 xml_lib = library(
     'xml2',
     files(xml_src),
@@ -485,8 +487,8 @@ xml_lib = library(
     dependencies: xml_deps,
     include_directories: config_dir,
     install: true,
-    version: meson.project_version(),
-    soversion: v_maj + v_min_compat,
+    version: f'@so_version@.@age@.@v_mic@',
+    soversion: so_version,
 )
 
 dep_inc = include_directories('include')