perl 5.003_07: Configure

perl 5.003_07: Configure

Detect GNU libc (thanks, Skimo!) and avoid nm if we have GNU libc.
Since the GNU libc test requires compiling and linking a test
program, the dependencies have been altered and lots of pieces of
Configure have moved around unchanged.  The patch is big but the
effect is little.

Allow for both <sys/select.h> and <time.h> in fd_set tests.
Systems which don't allow both (e.g. SCO) have to turn off one
or the other in the hints file for now.