log: Add locking to large logging blocks

Reuse the existing locking provided by stdio to keep in_asm, cpu,
op, op_opt, op_ind, and out_asm as contiguous blocks.

While it isn't possible to interleave e.g. in_asm or op_opt logs
because of the TB lock protecting all code generation, it is
possible to interleave cpu logs, or to interleave a cpu dump with
an out_asm dump.

For mingw32, we appear to have no viable solution for this.  The locking
functions are not properly exported from the system runtime library.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
diff --git a/cpu-exec.c b/cpu-exec.c
index 3e40886..4188fed 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -150,11 +150,13 @@
 #if defined(DEBUG_DISAS)
     if (qemu_loglevel_mask(CPU_LOG_TB_CPU)
         && qemu_log_in_addr_range(itb->pc)) {
+        qemu_log_lock();
 #if defined(TARGET_I386)
         log_cpu_state(cpu, CPU_DUMP_CCOP);
 #else
         log_cpu_state(cpu, 0);
 #endif
+        qemu_log_unlock();
     }
 #endif /* DEBUG_DISAS */