libsysprof: move tree.h to contrib/

Soon src/sysprof will use it as well.

contrib/meson.build

@@ -1,3 +1,4 @@
 subdir('eggbitset')
 subdir('elfparser')
 subdir('linereader')
+subdir('tree')

contrib/tree/meson.build

@@ -0,0 +1,7 @@
+libtree_deps = [
+  gio_dep,
+]
+
+libtree_static_dep = declare_dependency(
+  include_directories: include_directories('.'),
+)

src/libsysprof/meson.build

@@ -214,6 +214,7 @@ libsysprof_deps = [
   libeggbitset_static_dep,
   libelfparser_static_dep,
   liblinereader_static_dep,
+  libtree_static_dep,
   libsysprof_capture_dep,
 ]