Add a config.h for FreeBSD, generated by running "../configure" in third_party/libevent/freebsd/ on a FreeBSD 10.0-amd64 system.

For 32-bit FreeBSD systems, SIZEOF_LONG would be 4, but since both systems
have a strtoll() function this does not matter (see libevent/evutil.c).
Taking 8 for SIZEOF_LONG is also in sync with _EVENT_SIZEOF_LONG as
defined in libevent/freebsd/event-config.h

BUG=350396
TBR=cpu

Review URL: https://codereview.chromium.org/183803011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255766 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255766