scons: Remove references to u_thread.c

For future reference: always run "git grep" on refactorings.

src/mapi/glapi/SConscript

@@ -38,7 +38,6 @@ glapi_sources = [
 mapi_sources = [
     'u_current.c',
     'u_execmem.c',
-    'u_thread.c',
 ]
 for s in mapi_sources:
     o = env.SharedObject(s[:-2], '../mapi/' + s)

src/mapi/shared-glapi/SConscript

@@ -8,8 +8,14 @@ Import('*')
 def mapi_objects(env, printer, mode):
     """Return mapi objects built for the given printer and mode."""
     mapi_sources = {
-        'glapi': ['entry.c', 'mapi_glapi.c', 'stub.c', 'table.c',
-                  'u_current.c', 'u_execmem.c', 'u_thread.c'],
+        'glapi': [
+            'entry.c',
+            'mapi_glapi.c',
+            'stub.c',
+            'table.c',
+            'u_current.c',
+            'u_execmem.c',
+        ],
         'bridge': ['entry.c'],
     }
     mapi_defines = {

src/mapi/vgapi/SConscript

@@ -32,7 +32,6 @@ mapi_sources = [
     'table.c',
     'u_current.c',
     'u_execmem.c',
-    'u_thread.c',
 ]
 
 vgapi_objects = []