Fix two bugs and use the more efficient !empty() vs size() > 0

These two bugs were found with a recent cppcheck addition. It also
changes one occurrence of size() > 0 for the more efficient ! empty().

tgt-vhdl/stmt.cc

@@ -65,7 +65,7 @@ static int draw_stask_finish(vhdl_procedural *proc, stmt_container *container,
 static char parse_octal(const char *p)
 {
    assert(*p && *(p+1) && *(p+2));
-   assert(isdigit(*p) && isdigit(*(p+1)) && isdigit(*(p+1)));
+   assert(isdigit(*p) && isdigit(*(p+1)) && isdigit(*(p+2)));
 
    return (*p - '0') * 64
       + (*(p+1) - '0') * 8

tgt-vvp/eval_expr.c

@@ -3299,7 +3299,7 @@ static struct vector_info draw_unary_expr(ivl_expr_t expr, unsigned wid)
 		    /* Handle special case that value is 0 or 1. */
 		  if (res.base == 0 || res.base == 1)
 			break;
-		  if (res.base == 2 || res.base == 2) {
+		  if (res.base == 2 || res.base == 3) {
 			res.base = 0;
 			break;
 		  }

vhdlpp/architec_emit.cc

@@ -136,7 +136,7 @@ int ComponentInstantiation::emit(ostream&out, Entity*ent, Architecture*arc)
       int errors = 0;
 
       out << cname_;
-      if (generic_map_.size() > 0) {
+      if (! generic_map_.empty()) {
 	    out << " #(";
 	    comma = "";
 	    for (map<perm_string,Expression*>::iterator cur = generic_map_.begin()