check for and enable Large File Support automatically

If you try to process a file using a 32bit build that is larger than
2GiB in size, the linux kernel will reject things:
$ strace -eopen dump_syms ./chrome ./ > chrome.sym
...
open(".//chrome.debug", O_RDONLY)       = -1 EOVERFLOW (Value too large for defined data type)

So let's use the existing autoconf macro to check for and enable support
as need be.

We have to shift the existing m32 logic up to before we start doing
feature test macros though otherwise a simple configure won't work:
$ ./configure --enable-m32
This is because it first tests LFS and such w/out the -m32 flags.

BUG=chromium:266064
TEST=`./configure --enable-m32 && make && make check` passes
R=benchan@chromium.org

Review URL: https://breakpad.appspot.com/619002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1250 4c0a9323-5329-0410-9bdc-e9ce6186880e