8 different places were using __ImageBase to get the current module,
create a CURRENT_MODULE() macro that all these places can use.

All but one use of base::GetModuleFromAddress() were used to get
the module of the current file; change all these to use
CURRENT_MODULE() instead.

The (somewhat lame) motivation is that GetModuleFromAddress() took
a void* but was always called with function pointers, and converting
function pointers to void* has undefined behavior. POSIX (dlsym())
requires that conversions between void* and function pointers work
in practice, but on posix an explicit reinterpret_cast is required, and it
seems nice to have compilers behave identically between platforms
here (i.e. we should turn on clang/win's -Wmicrosoft-cast).

In the one place where GetModuleFromAddress() didn't refer to the
current TU's module, add an explicit reinterpret_cast.

BUG=550065
TBR=asvitkine,wez

Review URL: https://codereview.chromium.org/1852143...