gnu.cfg: Add support for pvalloc() and __builtin_alloca().

cfg/gnu.cfg

@@ -18,6 +18,12 @@
     <alloc init="true">backtrace_symbols</alloc>
     <dealloc>free</dealloc>
   </memory>
+  <memory>
+    <alloc init="false" buffer-size="arg-value:1">pvalloc</alloc>
+    <dealloc>free</dealloc>
+  </memory>
+  <!-- https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html -->
+  <define name="__builtin_alloca" value="alloca"/>
   <!-- void xexit(int status); -->
   <function name="xexit">
     <noreturn>true</noreturn>
@@ -77,6 +83,17 @@
       <not-bool/>
     </arg>
   </function>
+  <!-- https://linux.die.net/man/3/pvalloc -->
+  <!-- void *pvalloc(size_t size); -->
+  <function name="pvalloc">
+    <use-retval/>
+    <returnValue type="void *"/>
+    <noreturn>false</noreturn>
+    <arg nr="1" direction="in">
+      <not-uninit/>
+      <valid>0:</valid>
+    </arg>
+  </function>
   <!-- http://man7.org/linux/man-pages/man3/asprintf.3.html -->
   <!-- int asprintf(char **strp, const char *fmt, ...); -->
   <function name="asprintf">