Delete global_thread_pool

This was apparently used for parallel linking at some point but was
dummied out for mysterious reasons. Even without that, I suspect
that the thread pool wouldn't need to be global.

src/gctools/threadlocal.cc

@@ -25,9 +25,6 @@
 THREAD_LOCAL gctools::ThreadLocalStateLowLevel* my_thread_low_level;
 THREAD_LOCAL core::ThreadLocalState* my_thread;
 
-namespace gctools {
-thread_pool<ThreadManager>* global_thread_pool;
-};
 namespace core {
 
 #ifdef DEBUG_VIRTUAL_MACHINE
@@ -244,11 +241,7 @@ pid_t ThreadLocalState::safe_fork()
 {
   // Wrap fork in code that turns guards off and on
   this->_VM.disable_guards();
-  // shut down llvm thread pool
-  gctools::global_thread_pool->~thread_pool();
   pid_t result = fork();
-  // start up llvm thread pool
-  gctools::global_thread_pool = new thread_pool<ThreadManager>(thread_pool<ThreadManager>::sane_number_of_threads());
   if (result==-1) {
     // error
     printf("%s:%d:%s fork failed errno = %d\n", __FILE__, __LINE__, __FUNCTION__, errno );

src/llvmo/runtimeJit.cc

@@ -679,8 +679,8 @@ namespace llvmo {
 /*! Call this after fork() to create a thread-pool for lljit
  */
 CL_DEFUN void llvm_sys__create_lljit_thread_pool() {
-  gctools::global_thread_pool = new thread_pool<ThreadManager>(thread_pool<ThreadManager>::sane_number_of_threads());
 #if 0
+  gctools::global_thread_pool = new thread_pool<ThreadManager>(thread_pool<ThreadManager>::sane_number_of_threads());
   ClaspJIT_O* jit = &*gctools::As<ClaspJIT_sp>(_lisp->_Roots._ClaspJIT);
   jit->_LLJIT->getExecutionSession().setDispatchTask([jit](std::unique_ptr<Task> T) {
     DEBUG_OBJECT_FILES_PRINT(("%s:%d:%s pushing an LLJIT task\n", __FILE__, __LINE__, __FUNCTION__ ));