linux3.18: update to 3.18-rc4.
gmp: needs host m4 to build.
New package: gcc-4.7-4.7.3 exclusively for base-chroot-musl.
gzip: unbreak musl builds.
tar: unbreak musl builds.
base-chroot-musl: depend on gcc-4.7 to have a working build environment.
New package: i3blocks-1.3.
xbps-src: introduce build profiles and use it by default.

common/build-profiles contains the compilation flags used in native
builds, and are defined per architecture:

	- x86_64 (glibc)
	- x86_64-musl (musl)

If XBPS_CFLAGS or XBPS_CXXFLAGS are set in `etc/conf`, the settings
from the build profile will be overrided.
findutils: override some configure tests to unbreak musl builds.
xbps-src: also use build-profiles for bootstrap pkgs.
xbps-src: chroot: do nothing if we are already in the chroot.
xbps-src: new hook to remove misc files (used for musl currently).
srcpkgs: revbump some bootstrap pkgs to remove unwanted files (musl).
xbps-src: correct test behaviour for build-profiles.
python-pytz: update to 2014.9
python-Pygments: update to 2.0
base-system: on musl do not depend on glibc-locales :-)
autoconf: needs host m4 to build.
common/shlibs: add libintl.so.8 from gettext on !glibc builds.
btrfs-progs: update to 3.17.1; added patches for musl via Alpine.