[x86] Changes and Additions to fix broken x86 build

Add missing syscalls to android/libc/arch-x86/syscalls

Remove #undef HAVE_GETLINE from platform.h
Fixes definition conflict warnings for x86 but is also
suitable for arm as  bionic has had a getline implementation for a
while now

Remove hardcoded CONFIG_CROSS_COMPILER_PREFIX from .config-full
and .config-minimal. This is now appended to  .config as part of
the prepare target in Android.mk

It appears no other changes are needed to other files such as
bbconfigopts.h etc as these are autogenerated when make prepare
is run.

Android.mk:
Added missing syscalls source to BUSYBOX_SRC_FILES when
TARGET_ARCH=x86.
Added appending of the CONFIG_CROSS_COMPILER_PREFIX to the .config
file based on the TARGET_ARCH

Change-Id: I4f550757b3209b852cd5a017e88dce50678e5734
fstrim: sync with busybox master (now an official applet)

fstrim: Needs to fire at the mp, not bd

It's a filesystem thing from this perspective.

fstrim: Indicate failure on error

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

Change-Id: Icffb851cbe1895523e67e5ff18c67f9109a46a28
fstrim: use new-style config/kbuild/applet snippets; trim help text

function                                             old     new   delta
packed_usage                                       29546   29520     -26

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

Change-Id: I758c91f2054d1f2876fc1446f8f0afd8bffd2611