svndump.c: Fix a printf format compiler warning

svndump.c: Fix a printf format compiler warning

In particular, on systems that define uint32_t as an unsigned long,
gcc complains as follows:

        CC vcs-svn/svndump.o
    vcs-svn/svndump.c: In function `svndump_read':
    vcs-svn/svndump.c:215: warning: int format, uint32_t arg (arg 2)

In order to suppress the warning we use the C99 format specifier
macro PRIu32 from <inttypes.h>.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Acked-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>