Support for Clang with "-fgnuc-version=0". Previously, the code assumed that Clang pretends to be GCC and defines the __GNUC__ macro, which might not be the case if the "-fgnuc-version=0" flag is used. Fix is to explicitly check for __clang__ as well. In practice, with this change ngx_cpuinfo() is now available on Linux with "-fgnuc-version=0".

--- a/src/event/modules/ngx_iocp_module.c
+++ b/src/event/modules/ngx_iocp_module.c
@@ -172,7 +172,7 @@ ngx_iocp_timer(void *data)
 #endif
     }
 
-#if defined(__WATCOMC__) || defined(__GNUC__)
+#if defined(__WATCOMC__) || defined(__GNUC__) || defined(__clang__)
     return 0;
 #endif
 }