Add thread_db for gdb-7.7

mipsr6 (both 32-/64-bit) need gdb-7.7

Change-Id: I075866279ca5fa18424f5bbae3b3621415d976a7
Lower latency for AudioRecorder

Change-Id: Ibc4d89651a291a7c830761627105bfe4ac045b14
Floating-point data for AudioPlayer

Change-Id: I0da5394f9e4ff8bd714a6bbb54face0595b12ab2
NDK Programmer's Guide; NDK Getting Started

Change-Id: I918162aa0a9c2e18dd4c999ef21465df1b761705

Conflicts:
	docs/text/CPU-FEATURES.text
Correction for android API level L

Change-Id: I75467727f3f18cf7f7c018a502c5b7a0633621ca
Fix of gcc-sdk wrapper usage

Because the x86_64-linux-glibc2.7-4.6 and i686-linux-glibc2.7-4.6 were removed from prebuilts.
See Id: I9f1b24b1606ac11856bee796204bbf68cd3ef6be
We have to set __USE_OLD_LINUX_HOST_GCC=no

gcc-sdk wrapper became useless at all, because now,
we have only 64bit host toolchains for Linux.

Change-Id: I5faaec6f4b7e68ee12d882c7de6080091ce53dc2
Signed-off-by: Arseniy Antonov <arseniy.antonov@intel.com>
Handle split NDK package

Due to 512MB size limit on server which hosts NDK package for download,
each NDK packages in r10 is splitted into 2 pieces:

1) android-ndk32-r10* has the same directory structure as in the previous
   r9d release. The new android-L and gcc4.9 aren't here.
2) android-ndk64-r10* contains headers/tools for the new 64-bit ABIs:
   arm64-v8a, x86_64, and mips64, plus android-L and gcc4.9 for the
   existing 32-bit ABIs.
See b.android.com/73705

This CL slightly modify some rules in ndk-build

1) don't expand all, all32 and all64 to ABIs without toolchain.  This allows
   most examples with APP_ABI=all to compile out-of-box in each NDK pacakge
2) The default gcc for 32-bit is still gcc4.6, but can accept
   any gcc if that's what available.  This allows samples to be compiled in
   32-bit in android-ndk64-r10* package when only gcc-4.9 is available.

Also add libmediandk.so to system lib list

Change-Id: I8f4a5032184450f224252a10ca1fac6b840e39de