shared: make nm_streq() and nm_streq0() inline functions

There is no advantage in having these as macros. Make them
inline functions, compiler should be able to decide that they
are in fact inlinable.

Also, don't call g_strcmp0() for nm_streq0(). It means we first
have to call glib function, only to call a glibc function. No need
for this abstraction.

shared/nm-utils/nm-macros-internal.h

@@ -860,8 +860,18 @@ fcn (void) \
 
 /*****************************************************************************/
 
-#define nm_streq(s1, s2)  (strcmp (s1, s2) == 0)
-#define nm_streq0(s1, s2) (g_strcmp0 (s1, s2) == 0)
+static inline gboolean
+nm_streq (const char *s1, const char *s2)
+{
+	return strcmp (s1, s2) == 0;
+}
+
+static inline gboolean
+nm_streq0 (const char *s1, const char *s2)
+{
+	return    (s1 == s2)
+	       || (s1 && s2 && strcmp (s1, s2) == 0);
+}
 
 #define NM_STR_HAS_PREFIX(str, prefix) \
 	(strncmp ((str), ""prefix"", NM_STRLEN (prefix)) == 0)