qemu/atomic.h: rename atomic_ to qatomic_

clang's C11 atomic_fetch_*() functions only take a C11 atomic type
pointer argument. QEMU uses direct types (int, etc) and this causes a
compiler error when a QEMU code calls these functions in a source file
that also included <stdatomic.h> via a system header file:

  $ CC=clang CXX=clang++ ./configure ... && make
  ../util/async.c:79:17: error: address argument to atomic operation must be a pointer to _Atomic type ('unsigned int *' invalid)

Avoid using atomic_*() names in QEMU's atomic.h since that namespace is
used by <stdatomic.h>. Prefix QEMU's APIs with 'q' so that atomic.h
and <stdatomic.h> can co-exist. I checked /usr/include on my machine and
searched GitHub for existing "qatomic_" users but there seem to be none.

This patch was generated using:

  $ git grep -h -o '\<atomic\(64\)\?_[a-z0-9_]\+' include/qemu/atomic.h | \
    sort -u >/tmp/changed_identifiers
  $ for identifier in $(</tmp/changed_identifiers); do
        sed -i "s%\<$identifier\>%q$identifier%g" \
            $(git grep -I -l "\<$identifier\>")
    done

I manually fixed line-wrap issues and misaligned rST tables.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200923105646.47864-1-stefanha@redhat.com>
diff --git a/softmmu/cpu-throttle.c b/softmmu/cpu-throttle.c
index 4e6b281..2ec4b8e 100644
--- a/softmmu/cpu-throttle.c
+++ b/softmmu/cpu-throttle.c
@@ -64,7 +64,7 @@
         }
         sleeptime_ns = endtime_ns - qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
     }
-    atomic_set(&cpu->throttle_thread_scheduled, 0);
+    qatomic_set(&cpu->throttle_thread_scheduled, 0);
 }
 
 static void cpu_throttle_timer_tick(void *opaque)
@@ -77,7 +77,7 @@
         return;
     }
     CPU_FOREACH(cpu) {
-        if (!atomic_xchg(&cpu->throttle_thread_scheduled, 1)) {
+        if (!qatomic_xchg(&cpu->throttle_thread_scheduled, 1)) {
             async_run_on_cpu(cpu, cpu_throttle_thread,
                              RUN_ON_CPU_NULL);
         }
@@ -94,7 +94,7 @@
     new_throttle_pct = MIN(new_throttle_pct, CPU_THROTTLE_PCT_MAX);
     new_throttle_pct = MAX(new_throttle_pct, CPU_THROTTLE_PCT_MIN);
 
-    atomic_set(&throttle_percentage, new_throttle_pct);
+    qatomic_set(&throttle_percentage, new_throttle_pct);
 
     timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) +
                                        CPU_THROTTLE_TIMESLICE_NS);
@@ -102,7 +102,7 @@
 
 void cpu_throttle_stop(void)
 {
-    atomic_set(&throttle_percentage, 0);
+    qatomic_set(&throttle_percentage, 0);
 }
 
 bool cpu_throttle_active(void)
@@ -112,7 +112,7 @@
 
 int cpu_throttle_get_percentage(void)
 {
-    return atomic_read(&throttle_percentage);
+    return qatomic_read(&throttle_percentage);
 }
 
 void cpu_throttle_init(void)