unix: fix compilation errors when using the -pedantic flag

This commit fixes some errors that might arise when compiling
libuv with the pendanting. The error in question is
"ISO C90 forbids mixing declarations and code"

Closes: libuv#3131

src/unix/darwin.c

@@ -210,6 +210,7 @@ static int uv__get_cpu_speed(uint64_t* speed) {
   void* core_foundation_handle;
   void* iokit_handle;
   int err;
+  CFMutableDictionaryRef classes_to_match;
 
   kern_return_t kr;
   mach_port_t mach_port;
@@ -257,8 +258,7 @@ static int uv__get_cpu_speed(uint64_t* speed) {
 
   kr = pIOMasterPort(MACH_PORT_NULL, &mach_port);
   assert(kr == KERN_SUCCESS);
-  CFMutableDictionaryRef classes_to_match
-      = pIOServiceMatching("IOPlatformDevice");
+  classes_to_match = pIOServiceMatching("IOPlatformDevice");
   kr = pIOServiceGetMatchingServices(mach_port, classes_to_match, &it);
   assert(kr == KERN_SUCCESS);
   service = pIOIteratorNext(it);

src/unix/udp.c

@@ -954,8 +954,8 @@ static int uv__udp_set_source_membership6(uv_udp_t* handle,
     mreq.gsr_interface = 0;
   }
 
-  STATIC_ASSERT(sizeof(mreq.gsr_group) >= sizeof(*multicast_addr));
-  STATIC_ASSERT(sizeof(mreq.gsr_source) >= sizeof(*source_addr));
+  assert(sizeof(mreq.gsr_group) >= sizeof(*multicast_addr));
+  assert(sizeof(mreq.gsr_source) >= sizeof(*source_addr));
   memcpy(&mreq.gsr_group, multicast_addr, sizeof(*multicast_addr));
   memcpy(&mreq.gsr_source, source_addr, sizeof(*source_addr));