Turn some license strings into lib.licenses values

pkgs/development/tools/profiling/oprofile/default.nix

@@ -47,7 +47,7 @@ stdenv.mkDerivation rec {
       is profiled: hardware and software interrupt handlers, kernel
       modules, the kernel, shared libraries, and applications.
     '';
-    license = "GPLv2";
+    license = stdenv.lib.licenses.gpl2;
     homepage = http://oprofile.sourceforge.net/;
 
     platforms = stdenv.lib.platforms.linux;

pkgs/development/tools/profiling/sysprof/default.nix

@@ -14,7 +14,7 @@ stdenv.mkDerivation rec {
   meta = {
     homepage = http://sysprof.com/;
     description = "Sysprof, a system-wide profiler for Linux";
-    license = "GPLv2+";
+    license = stdenv.lib.licenses.gpl2Plus;
 
     longDescription = ''
       Sysprof is a sampling CPU profiler for Linux that uses the perf_event_open

pkgs/development/tools/profiling/systemtap/default.nix

@@ -65,7 +65,7 @@ stdenv.mkDerivation rec {
 
     homepage = http://sourceware.org/systemtap/;
 
-    license = "GPLv2+";
+    license = stdenv.lib.licenses.gpl2Plus;
 
     maintainers = [ ];
     platforms = stdenv.lib.platforms.linux;