mesa: use a prefix for the program lex

mesa: use a prefix for the program lex

This avoids us making a global yylex symbol which will interfere will
all sorts of apps.

with libdricore which can't do symbol visibility currently we pollute
the namespace with this.

This is a candidate for 9.0 & stable branches.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>