[sqlite] sqlite3rbu.c: ANSI C incomatible variable delcaration

[Ralf Junker]

sqlite3rbu.c intermingles variable declaration and code, which is not 
with ANSI C here:

http://www.sqlite.org/src/artifact/d37e1ca2d13e439c?ln=623-624

Declaring zSql before calling va_start() solves the problem for me:

   char *zSql;
   va_start(ap, zFmt);
   zSql = sqlite3_vmprintf(zFmt, ap);

Ralf