Reduce build warnings and enable Qt build

src/leveldb/port/port_posix.cc

@@ -55,8 +55,10 @@ void InitOnce(OnceType* once, void (*initializer)()) {
 
 bool HasAcceleratedCRC32C() {
 #if (defined(__x86_64__) || defined(__i386__)) && defined(__GNUC__)
-  unsigned int eax, ebx, ecx, edx;
-  __get_cpuid(1, &eax, &ebx, &ecx, &edx);
+  unsigned int eax = 0, ebx = 0, ecx = 0, edx = 0;
+  if (__get_cpuid(1, &eax, &ebx, &ecx, &edx) == 0) {
+    return false;
+  }
   return (ecx & (1 << 20)) != 0;
 #else
   return false;

src/leveldb/util/logging.cc

@@ -55,7 +55,7 @@ bool ConsumeDecimalNumber(Slice* in, uint64_t* val) {
       const int delta = (c - '0');
       static const uint64_t kMaxUint64 = ~static_cast<uint64_t>(0);
       if (v > kMaxUint64/10 ||
-          (v == kMaxUint64/10 && delta > kMaxUint64%10)) {
+          (v == kMaxUint64/10 && static_cast<uint64_t>(delta) > kMaxUint64%10)) {
         // Overflow
         return false;
       }