libc/uClibc: add additional debug level between "minimal" and "all"

During application development it is desirable to enable malloc
debugging and LD_DEBUG support, but the extensive debug spew from
SUPPORT_LD_DEBUG_EARLY is only useful when working on
uClibc's ld.so.

Signed-off-by: Johannes Stezenbach <js@sig21.net>

reporter_name="Dragan Marinkovic <marinkovic.dragan@gmail.com>"

reporter_url=""

reporter_comment=""