Don't hardcode the valid architectures in one xcode project

There's no reason to hardcode these here - these are the default.
(We keep the intentionally hardcoded default arch in the
codec_unittest project though.)
Use default paths for and object files and other intermediate files

This makes sure that one can build for all architectures without
having the intermediates from one clobber the other.
Remove outdated advice from the readme

We no longer use the GCCVERSION variable - we let the NDK pick whichever
compiler version is the default for the chosen architecture.
Remove unused includes of sys/timeb.h

This header is included by crt_util_safe_x.h whenever necessary (it's
all hidden in the SWelsTime struct) - code which does not explicitly
use things from sys/timeb.h shouldn't include it.
Manually define the SWelsTime struct on unix, don't rely on struct timeb

We don't use the ftime function on unix for filling SWelsTime anyway,
we fill the time and millitm fields manually.

On android, the sys/timeb.h header has been removed in the next
platform version (currently available in NDK r10 in the "L preview"
release), since this header and the ftime function have been removed
from the POSIX 2008 specification.

This fixes compilation when targeting the Android "L preview" release,
even when targeting the 32 bit ABIs.
Add support for building for the new 64 bit android ABIs

This requires the new NDK r10.

The mips64 ABI is handled by the default case, there's no need to
add custom code for that in platform-android.mk.
Fix incorrect indentation in build/platform-android.mk
Set the encDemo header paths on the target level

Currently half of them are set on the project level, and half of them
on the target level.

In all other projects within OpenH264, they're set on the target level.
Merge pull request #1130 from mstorsjo/default-intermediates-path

Use default paths for and object files and other intermediate files
Merge pull request #1148 from mstorsjo/dont-hardcode-xcode-archs

Don't hardcode the valid architectures in one xcode project
Use macros for setting the output directory

This makes sure this is set to the exact same string in all
the configurations, simplifying editing multiple configurations
at the same time.

This changes the output directory for 64 bit binaries from
bin/win64 to bin/x64, but this is the common pattern used by
MSVC in new projects.
Merge pull request #1185 from mstorsjo/android-l-preview

Fix building for the Android L preview release, add support for new 64 bit Android ABIs
Merge pull request #1194 from mstorsjo/msvc-simplify-output-dirs

Use macros for setting the output directory in MSVC project files
Merge pull request #1191 from mstorsjo/merge-encdemo-include-paths

Set the encDemo header paths on the target level
Merge remote-tracking branch 'upstream/master' into travis.osx