gnu.cfg: Added support for isascii_l(), which is a GNU-extension.

cfg/gnu.cfg

@@ -185,6 +185,21 @@
       <not-uninit/>
     </arg>
   </function>
+  <!-- int isascii_l(int c, locale_t locale); -->
+  <function name="isascii_l">
+    <use-retval/>
+    <pure/>
+    <returnValue type="int">arg1&gt;=0 &amp;&amp; arg1&lt;=0x7F</returnValue>
+    <noreturn>false</noreturn>
+    <leak-ignore/>
+    <arg nr="1" direction="in">
+      <not-uninit/>
+      <valid>0:255</valid>
+    </arg>
+    <arg nr="2" direction="in">
+      <not-uninit/>
+    </arg>
+  </function>
   <!-- http://man7.org/linux/man-pages/man3/asprintf.3.html -->
   <!-- int vasprintf(char **strp, const char *fmt, va_list ap); -->
   <function name="vasprintf">