configure: do not use '@' in version string

Using an '@' in the version string breaks the gcc/glibc/gdb manuals.
Use a scheme similar to Debian, with a plus '+' instead of the '@',
as suggested by Michael Hope.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 reporter_name="YEM"

 reporter_url="http://ymorin.is-a-geek.org/"

 reporter_comment="EXPERIMENTAL Super-H sh4 sample."