remove gcc49 overrides from various places

An interesting thing is that: stdenv != overrideCC stdenv gcc49;
I'm not sure why that is, but it doesn't seem important.

/cc maintainers: @nckx, @garbas, @abbradar, @cstrahan, @grwlf.

(cherry picked from commit 3064b6a0cc4dc047fae97bdffa0725bc7fd38f2e)

pkgs/development/libraries/bobcat/default.nix

···
-{ stdenv, fetchurl, gcc49, icmake, libmilter, libX11, openssl, readline
+{ stdenv, fetchurl, icmake, libmilter, libX11, openssl, readline
 , utillinux, yodl }:
 
 let version = "3.25.02"; in
···
     maintainers = with maintainers; [ nckx ];
   };
 
-  buildInputs = [ gcc49 libmilter libX11 openssl readline utillinux ];
+  buildInputs = [ libmilter libX11 openssl readline utillinux ];
   nativeBuildInputs = [ icmake yodl ];
 
   postPatch = ''

pkgs/development/tools/parsing/flexc++/default.nix

···
-{ stdenv, fetchurl, bobcat, gcc49, icmake, yodl }:
+{ stdenv, fetchurl, bobcat, icmake, yodl }:
 
 let version = "2.02.00"; in
 stdenv.mkDerivation rec {
···
     maintainers = with maintainers; [ nckx ];
   };
 
-  buildInputs = [ bobcat gcc49 ];
+  buildInputs = [ bobcat ];
   nativeBuildInputs = [ icmake yodl ];
 
   postPatch = ''

pkgs/os-specific/linux/jfbview/default.nix

···
-# FIXME: remove gcc49 when the default gcc supports C++1y
-{ stdenv, fetchFromGitHub, freetype, gcc49, imlib2, jbig2dec, libjpeg, libX11
+{ stdenv, fetchFromGitHub, freetype, imlib2, jbig2dec, libjpeg, libX11
 , mujs, mupdf, ncurses, openjpeg, openssl }:
 
 let
···
     owner = "jichu4n";
   };
 
-  buildInputs = [ freetype gcc49 imlib2 jbig2dec libjpeg libX11 mujs mupdf
+  buildInputs = [ freetype imlib2 jbig2dec libjpeg libX11 mujs mupdf
     ncurses openjpeg openssl ];
 
   buildFlags = binaries;

pkgs/top-level/all-packages.nix

···
 
   torbutton = callPackage ../tools/security/torbutton { };
 
-  torbrowser = callPackage ../tools/security/tor/torbrowser.nix {
-    stdenv = overrideCC stdenv gcc49;
-  };
+  torbrowser = callPackage ../tools/security/tor/torbrowser.nix { };
 
   touchegg = callPackage ../tools/inputmethods/touchegg { };
 
···
   clipit = callPackage ../applications/misc/clipit { };
 
   bomi = callPackage ../applications/video/bomi {
-    stdenv = overrideCC stdenv gcc49;
     pulseSupport = config.pulseaudio or true;
   };
 
···
   zathuraCollection = recurseIntoAttrs
     (let callPackage = newScope pkgs.zathuraCollection; in
       import ../applications/misc/zathura {
-        inherit callPackage pkgs fetchurl lib;
-        stdenv = overrideCC stdenv gcc49;
+        inherit stdenv callPackage pkgs fetchurl lib;
         useMupdf = config.zathura.useMupdf or false;
       });
 
···
 
   girara = callPackage ../applications/misc/girara {
     gtk = gtk3;
-    stdenv = overrideCC stdenv gcc49;
   };
 
   girara-light = callPackage ../applications/misc/girara {