hostrange_pop()/hostrange_shift(): test for overflow

hostrange_pop():				   
 * retrofitted out_of_memory() test after strdup;
 * tested for negative length/overflow before the while-loop,
   making sure that 'dims' characters also fit in;
 * second snprintf is not tested.

hostrange_shift(): 
 * analogous changes (second snprintf also not tested). 

host_prefix_end(): save variable, factor out common expressions

This saves one variable and factors out the condition common
to the if/else branches.06_hostlist__host_prefix_end.diff

 * return type of strlen is unsigned (size_t), hence strlen(hostname) >= 0;
 * both while-loops require idx >= 0, hence -1 is returned
   if strlen(hostname) == 0.

_get_bracketed_list(): simplify and look for overflow conditions
		       
 * initial test requires that len + 4 < n,
   - this ensures enough space for '[', ']', one digit and '\0',
   - simplifies many subsequent tests (e.g. for bracket_needed);
 * loop has been reorganized:
   - pre-condition:       len + 3 < n
   - loop run-condition:  len < n-1
   - post-condition:      len < n-1 (otherwise, it returns n);
 * therefore len < n after adding ']'
 * and thus len < n when calling buf[len] = '\0'.

hostrange_numstr(): overflow cases

This checks hostrange_numstr() for overflow cases:		    
 * requires n > dims (if dims=1, min 1 digit, else dim + '\0' digits);
   - this precondition simplifies many subsequent checks and
   - addresses if (len == n) then len++ means buf[len] = buf[n];
 * also checks return value of the snprintfs.

_hostrange_string()/hostlist_next(): test for overrun

This lets the two functions _hostrange_string/hostlist_next return NULL in case
there is an overflow condition.

Two possible overflow conditions were analyzed:
 * if len <= MAXHOSTNAMELEN + 15 and the '=' is the case, then len++ means
   that buf[len] = '\0' is the same as buf[MAXHOSTNAMELEN + 16], which would
   cause a segmentation violation - fixed by checking length beforehand;
 * also checks the return value of the snprintfs,
 * and requires 'dims' as minimum suffix length.

hostlist: let hostlist_get_base() depend on current dimensions

This patch saves one call to slurmdb_setup_cluster_dims(): exploiting
that the dimensions for which hostlist_get_base() is called are known
in all contexts in which the function is used.

hostlist: shorter conversion

This replaces the hostlist_parse_int_to_array() routine with a simpler and 
equivalent routine. I was wondering what the algorithm does, when suddenly
the flow became simpler.

Problem: we want to create an array 'out' of 'dims' dimensions where
         out[i], 0 <= i < dims, has the coefficients a_j of the polynomial

	 a_(dims-1) * B^(dims-1) + ... + a_1 * B + a_0

	 where B is the base of the polynomial 'in' and
	    a_0        = out[dims - 1]
	    a_1        = out[dims - 2]
	    ...
	    a_(dims-1) = a[0]

Using the Horner Scheme, 'in' is represented as
 * dims = 1:                                   a_0 = out[0]
 * dims = 2:                        a_1  * B + a_0 = out[0] * B + out[1]
 * dims = 3:            (a_2  * B + a_1) * B + a_0 
 * dims = 4: ((a_3 * B + a_2) * B + a_1) * B + a_0
   ...
 * dims = n: ((a_(n-1) * B + a_(n-2)) * B ... + a_1) * B + a_0

We can get a_0 = out[dims-1] as "in % B" and then derive a_1, a_2, ... by
first dividing by B, and then repeating the process.

If in is 0, all 'dims' coefficients are 0, if it is negative, all coefficients
are negative.

Added that when a slurmctld closes the connection to the database it's registered host and port are removed.

added semi-support for cgywin systems.  The slurmctld doesn't work becuase it exports symbols to the dll's and dll'
s can't import things like that.  But things should compile correctly and user tools like sview appear to work corr
ectly.

OK, this will probably where this part of the project stops since I can't figure out how to have the dll's in windo
ws grab the symbols from the slurmctld (like part_list).  It just uses the private value which isn't what we want.
 Things like sview and such work fine though.  (In cygwin the slurmd gets the name in all uppercase so you have to define it that way)