libuuid: remove _SVID_SOURCE pre-processor definition

libuuid: remove _SVID_SOURCE pre-processor definition

The _SVID_SOURCE is deprecated.

In file included from /usr/include/stdio.h:27:0,
                 from libuuid/src/gen_uuid.c:46: /usr/include/features.h:148:3:
		      warning: #warning "_BSD_SOURCE and _SVID_SOURCE are
		      deprecated, use _DEFAULT_SOURCE" [-Wcpp]

Notice that the Makefile.am has

AM_CPPFLAGS = \
        -include config.h \

that enforces the config.h is included before any other hearer.  In the
configure.ac there is AC_USE_SYSTEM_EXTENSIONS that makes all possible
features that can be supported in a system are turned on.  With these two
there is absolutely no need for any legacy _SOURCE definitions.

Reference: https://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commit;h=c941736c92fa3a319221f65f6755659b2a5e0a20
Signed-off-by: Sami Kerola <kerolasa@iki.fi>