Several compilation and run-time problems occur when building on SGI

IRIX systems using the native compilers.  A summary is:
- Various files use "//" as a comment delimiter in c files.
- Problems caused by assuming "char" is signed.
  cash.in: building -signed the rules regression test fails as described
    in FAQ_QNX4.  If CHAR_MAX is "255U" then ((signed char)CHAR_MAX) is -1.
  postmaster.c: random number regression test failed without this change.
- Some generic build issues and warning message cleanup.

David Kaelbling

src/interfaces/odbc/columninfo.c

@@ -144,12 +144,12 @@ CI_set_field_info(ColumnInfoClass *self, int field_num, char *new_name,
                                       Oid new_adtid, Int2 new_adtsize, Int4 new_atttypmod)
 {
     
-	// check bounds
+	/* check bounds */
 	if((field_num < 0) || (field_num >= self->num_fields)) {
 		return;
 	}
 
-	// store the info
+	/* store the info */
 	self->name[field_num] = strdup(new_name);  
 	self->adtid[field_num] = new_adtid;
 	self->adtsize[field_num] = new_adtsize;