Make integral serialization nothrow

Author: AndrejMitrovic

src/google/protobuf/encoding.d

@@ -61,6 +61,14 @@ unittest
     assert((-1L).toProtobuf!(Wire.zigzag).array == [0x01]);
 }
 
+nothrow unittest
+{
+    cast(void)toProtobuf(byte(1));
+    cast(void)toProtobuf(short(1));
+    cast(void)toProtobuf(int(1));
+    cast(void)toProtobuf(long(1));
+}
+
 auto toProtobuf(T)(T value)
 if (isFloatingPoint!T)
 {

src/google/protobuf/internal.d

@@ -10,7 +10,7 @@ struct Varint
     private ubyte index;
     private ubyte _length;
 
-    this(long value)
+    this(long value) nothrow
     out { assert(_length > 0); }
     do
     {