Setting the stdenv compiler to gcc 4.7.
Fixing the gcc47 build in stdenv

gcc 4.7 wants an explicit reference to the system include directory,
and that's guessed through 'stdenv ? glibc'.
Merge branch 'stdenv-updates' into stdenv-updates-gcc47
ARMv7 seems to need special ARM unpacking procedure, too
Not all parenthesis are extraneous, after all
ARMv7l fails in strange way with ARMv5 bootstrap but works with ARMv6 bootstrap
Merge branch 'stdenv-updates' into stdenv-updates-gcc47.
gmp: version 5.1.0 has the cpu-id patch applied already
gmp: switch default version back to 5.0.5

The 5.1.0 version breaks the build of virtually every package that uses the C++
wrappers for gmp (such as mpfr, ppl, etc).
all-packages.nix: strip trailing whitespace
ppl: update to version 0.12.1
mpfr: update to version 3.1.1
mpc: update to version 1.0.1
gmp: add back the cpuid patch to 5.0.5

it was lost during 5.0.5 -> 5.1.0 -> 5.1.0 w/o patch -> 5.0.5 w/o patch
buildNativeInputs -> nativeBuildInputs
Enable mcrypt, intl and exif support in PHP
php: Add xsl optional support

Use an override with xsl = true to enable xsl support in php.
php: Add mcrypt optional support

Use an override with mcrypt = true to enable libmcrypt support in php.
The --disable-posix-threadsds mcrypt build option was required by php.
php: Add zip and optional bz2 support

Use the overload bz2 = true to enable bz2 support for php.
zip support is enabled by default as it doesn't require any library.
vlada/xfce

Major Xfce refactoring, also adding versions 4.10.*

Signed-off-by: Vladimír Čunát <vcunat@gmail.com>