Fix warnings encountered in MSVC build of gtest/gmock tests

This fixes these warnings:

…\gtest\googletest\test\gtest-port_test.cc(78) : error C2220: warning treated as error - no 'object' file generated
…\gtest\googletest\test\gtest-port_test.cc(78) : warning C4309: 'static_cast' : truncation of constant value
…\gtest\googletest\test\gtest-port_test.cc(79) : warning C4309: 'static_cast' : truncation of constant value

…\gtest\googlemock\test\gmock-matchers_test.cc(2712) : error C2220: warning treated as error - no 'object' file generated

…\gtest\googlemock\test\gmock-matchers_test.cc(2706) : while compiling class template member function 'testing::gmock_matchers_test::FloatingPointTest<float>::FloatingPointTest(void)'
…\gtest\googlemock\test\gmock-matchers_test.cc(2896) : see reference to function template instantiation 'testing::gmock_matchers_test::FloatingPointTest<float>::FloatingPointTest(void)' being compiled
…\gtest\googlemock\test\gmock-matchers_test.cc(2896) : see reference to class template instantiation 'testing::gmock_matchers_test::FloatingPointTest<float>' being compiled

…\gtest\googlemock\test\gmock-matchers_test.cc(2712) : warning C4267: 'argument' : conversion from 'size_t' to 'const unsigned int', possible loss of data
…\gtest\googlemock\test\gmock-matchers_test.cc(2714) : warning C4267: 'argument' : conversion from 'size_t' to 'const unsigned int', possible loss of data
…\gtest\googlemock\test\gmock-matchers_test.cc(2716) : warning C4267: 'argument' : conversion from 'size_t' to 'const unsigned int', possible loss of data
…\gtest\googlemock\test\gmock-matchers_test.cc(2717) : warning C4267: 'argument' : conversion from 'size_t' to 'const unsigned int', possible loss of data
…\gtest\googlemock\test\gmock-matchers_test.cc(2718) : warning C4267: 'argument' : conversion from 'size_t' to 'const unsigned int', possible loss of data
…\gtest\googlemock\test\gmock-matchers_test.cc(2721) : warning C4267: 'argument' : conversion from 'size_t' to 'const unsigned int', possible loss of data
…\gtest\googlemock\test\gmock-matchers_test.cc(2723) : warning C4267: 'argument' : conversion from 'size_t' to 'const unsigned int', possible loss of data