Captialize meta.description of all packages

In line with the Nixpkgs manual.

A mechanical change, done with this command:

  find pkgs -name "*.nix" | \
      while read f; do \
          sed -e 's/description\s*=\s*"\([a-z]\)/description = "\u\1/' -i "$f"; \
      done

I manually skipped some:

* Descriptions starting with an abbreviation, a user name or package name
* Frequently generated expressions (haskell-packages.nix)

pkgs/development/compilers/emscripten-fastcomp/default.nix

@@ -38,7 +38,7 @@ stdenv.mkDerivation rec {
 
   meta = with stdenv.lib; {
     homepage = https://github.com/kripken/emscripten-fastcomp;
-    description = "emscripten llvm";
+    description = "Emscripten llvm";
     platforms = platforms.all;
     maintainers = with maintainers; [ qknight matthewbauer ];
     license = stdenv.lib.licenses.ncsa;