util/String{Compare,API}: add more "noexcept"

src/util/StringAPI.hxx

@@ -140,7 +140,7 @@ StringIsEqual(const char *a, const char *b, size_t length) noexcept
  */
 gcc_malloc gcc_nonnull_all
 static inline char *
-DuplicateString(const char *p)
+DuplicateString(const char *p) noexcept
 {
 	return strdup(p);
 }

src/util/StringCompare.hxx

@@ -38,7 +38,7 @@
 #endif
 
 static inline bool
-StringIsEmpty(const char *string)
+StringIsEmpty(const char *string) noexcept
 {
 	return *string == 0;
 }

src/util/WStringCompare.hxx

@@ -35,7 +35,7 @@
 #include <wchar.h>
 
 static inline bool
-StringIsEmpty(const wchar_t *string)
+StringIsEmpty(const wchar_t *string) noexcept
 {
 	return *string == 0;
 }