feat: preventing possible future units crash when using namespace std;

Resolves #317

src/systems/angular/CMakeLists.txt

@@ -22,4 +22,4 @@
 
 cmake_minimum_required(VERSION 3.19)
 
-add_units_module(angular DEPENDENCIES mp-units::isq HEADERS include/units/systems/angular/angular.h)
+add_units_module(angular DEPENDENCIES mp-units::isq HEADERS include/mp_units/systems/angular/angular.h)

src/systems/angular/include/mp_units/systems/angular/angular.h

@@ -22,11 +22,11 @@
 
 #pragma once
 
-#include <units/dimension.h>
-#include <units/quantity_spec.h>
-#include <units/unit.h>
+#include <mp_units/dimension.h>
+#include <mp_units/quantity_spec.h>
+#include <mp_units/unit.h>
 
-namespace units::angular {
+namespace mp_units::angular {
 
 // clang-format off
 inline constexpr struct dim_angle : base_dimension<"A"> {} dim_angle;
@@ -52,4 +52,4 @@ inline constexpr auto deg2 = square<degree>;
 
 }  // namespace unit_symbols
 
-}  // namespace units::angular
+}  // namespace mp_units::angular