posix.cfg: Improved support for nice(). (danmar#7135)

Reference: https://www.man7.org/linux/man-pages/man2/nice.2.html

Author: orbitcowboy

cfg/posix.cfg

@@ -1942,6 +1942,7 @@ The function 'mktemp' is considered to be dangerous due to race conditions and s
     <arg nr="1">
       <not-uninit/>
       <not-bool/>
+      <valid>-20:19</valid>
     </arg>
   </function>
   <!-- int pause(void); -->

test/cfg/posix.c

@@ -1496,3 +1496,13 @@ void ctime_r_test(const time_t * timep, char * bufSizeUnknown)
     // cppcheck-suppress ctime_rCalled
     ctime_r(timep, bufSizeUnknown);
 }
+
+void invalidFunctionArg_nice(int inc)
+{
+    // cppcheck-suppress invalidFunctionArg
+    nice(-21);
+    nice(-20);
+    nice(19);
+    // cppcheck-suppress invalidFunctionArg
+    nice(+20);
+}