libnum: rename the namespace [num] -> [libnum]

The first name would make `num` on its own ambiguous when using the
namespace.

libnum/include/num/num.h

@@ -27,7 +27,7 @@
 #include <type_traits>
 #include <concepts>
 
-namespace num {
+namespace libnum {
 
 struct num8;
 struct num16;

libnum/src/str.cpp

@@ -1,5 +1,5 @@
 #include <num/num.h>
-using namespace num;
+using namespace libnum;
 
 /* Digits of the decimal part, from most to least significant. Returns the
    number of digits (which is 0 when x=0) */

libnum/test/isel_num16.cpp

@@ -1,5 +1,5 @@
 #include <num/num.h>
-using namespace num;
+using namespace libnum;
 
 extern "C" {
 

libnum/test/isel_num32.cpp

@@ -1,5 +1,5 @@
 #include <num/num.h>
-using namespace num;
+using namespace libnum;
 
 extern "C" {
 

libnum/test/isel_num8.cpp

@@ -1,6 +1,6 @@
 #include <num/num.h>
 
-using namespace num;
+using namespace libnum;
 
 extern "C" {
 

libnum/test/unit_sample.h

@@ -25,7 +25,7 @@
 #include <stdint.h>
 
 #include <num/num.h>
-using namespace num;
+using namespace libnum;
 
 //---
 // Integer sampling

libnum/test/unit_static.cpp

@@ -6,7 +6,7 @@
 // unit_static.cpp: Compile-time evaluation tests
 
 #include <num/num.h>
-using namespace num;
+using namespace libnum;
 
 static_assert(sizeof(num8) == 1);
 static_assert(sizeof(num16) == 2);