Tune up fix for autoconf 2.72 In #158, the build for gmime was corrected for autoconf version 2.72, which treats ac_cv_sys_file_offset_bits differently. (see de4f1b044141df3ef0b1fc20be422dc667443484)
This fix should make gmime keep building on systems that use older version of autoconf, not just 2.72 or later.
