Define uint64 and int64 using long long.

This is to avoid typedef collisions with some compile configurations.
For more info, see
https://blogs.oracle.com/nike/entry/ilp64_lp64_llp64
http://www.unix.org/whitepapers/64bit.html

BUG=4497

Review URL: https://codereview.webrtc.org/1186093004

Cr-Commit-Position: refs/heads/master@{#9451}
diff --git a/webrtc/base/basictypes_unittest.cc b/webrtc/base/basictypes_unittest.cc
index 20515ec..3ac4337 100644
--- a/webrtc/base/basictypes_unittest.cc
+++ b/webrtc/base/basictypes_unittest.cc
@@ -14,6 +14,15 @@
 
 namespace rtc {
 
+static_assert(sizeof(int8) == 1, "Unexpected size");
+static_assert(sizeof(uint8) == 1, "Unexpected size");
+static_assert(sizeof(int16) == 2, "Unexpected size");
+static_assert(sizeof(uint16) == 2, "Unexpected size");
+static_assert(sizeof(int32) == 4, "Unexpected size");
+static_assert(sizeof(uint32) == 4, "Unexpected size");
+static_assert(sizeof(int64) == 8, "Unexpected size");
+static_assert(sizeof(uint64) == 8, "Unexpected size");
+
 TEST(BasicTypesTest, Endian) {
   uint16 v16 = 0x1234u;
   uint8 first_byte = *reinterpret_cast<uint8*>(&v16);