Version pkgconfig, headers, and library for parallel installation

Since wlroots almost always significantly breaks API each minor release,
allowing parallel installation of wlroots helps packagers deal with
programs that require conflicting versions of wlroots.

Closes: #3786

include/meson.build

@@ -28,7 +28,7 @@ if not features.get('session')
 endif
 
 install_subdir('wlr',
-	install_dir: get_option('includedir'),
+	install_dir: get_option('includedir') / versioned_name,
 	exclude_files: exclude_files,
 )
 

include/wlr/meson.build

@@ -22,4 +22,4 @@ ver_h = configure_file(
 	configuration: version_data,
 )
 
-install_headers(conf_h, ver_h, subdir: 'wlr')
+install_headers(conf_h, ver_h, subdir: versioned_name / 'wlr')

meson.build

@@ -14,8 +14,7 @@ project(
 version = meson.project_version().split('-')[0]
 version_major = version.split('.')[0]
 version_minor = version.split('.')[1]
-assert(version_major == '0')
-soversion = version_minor.to_int() - 5
+versioned_name = '@0@-@1@.@2@'.format(meson.project_name(), version_major, version_minor)
 
 little_endian = target_machine.endian() == 'little'
 big_endian = target_machine.endian() == 'big'
@@ -175,8 +174,7 @@ wlr_inc = include_directories('include')
 symbols_file = 'wlroots.syms'
 symbols_flag = '-Wl,--version-script,@0@/@1@'.format(meson.current_source_dir(), symbols_file)
 lib_wlr = library(
-	meson.project_name(), wlr_files,
-	soversion: soversion.to_string(),
+	versioned_name, wlr_files,
 	dependencies: wlr_deps,
 	include_directories: [wlr_inc],
 	install: true,
@@ -208,7 +206,9 @@ endif
 pkgconfig = import('pkgconfig')
 pkgconfig.generate(
 	lib_wlr,
+	name: versioned_name,
 	description: 'Wayland compositor library',
+	subdirs: versioned_name,
 	url: 'https://gitlab.freedesktop.org/wlroots/wlroots',
 	variables: wlr_vars,
 )