Fix minidump_module_writer_test 32-bit x86 build

Fix minidump_module_writer_test 32-bit x86 build.

time_t is a typedef for long on Mac OS X. In 32-bit x86 (ILP32), long is
a signed 32-bit quantity, and its range does not contain the range of
uint32_t, used to store times in time_t fashion in minidump files. A
cast is necessary to make these EXPECT_* macros do the right thing. This
is not a problem in x86_64 (LP64) where long is a signed 64-bit
quantity, which does contain the range of uint32_t.

clang’s error was “error: comparison of integers of different signs:
'const long' and 'const unsigned int' [-Werror,-Wsign-compare]”

BUG=
R=rsesek@chromium.org

Committed: https://chromium.googlesource.com/crashpad/crashpad/+/9168ba47acf7

[Mark Mentovai, 2014-08-20 22:30:03]

Broken out from https://codereview.chromium.org/493563002.

[Robert Sesek, 2014-08-20 22:31:32]

lgtm

[Mark Mentovai, 2014-08-20 22:32:10]

Committed patchset #1 manually as 9168ba47acf7 (presubmit successful).