tor_snprintf instead of snprintf

Several places call 'snprintf' from stdio.h instead of 'tor_snprintf' from common/compat.h. Replacing them removes one dependency that complicates Windows nmake builds.

Complete list of occurences: src/common/util.c (<= 0.2.3.24-rc) src/or/routerparse.c src/ext/eventdns.c src/ext/OpenBSD_malloc_Linux.c src/ext/tinytest.c

Also, since the Microsoft _snprintf function has nonstandard semantics (which is why they renamed it), doing "#define snprintf _snprintf", as in src/or/or.h and src/common/compat.h is okay, but not so great.

Similarly, 'vsnprintf' could be replaced by 'tor_vsnprintf' in two places, which would simplify the #ifdefing going on.

Trac:
Username: ultramage