porting jpeg_mem_src() from jpeg lib v8c

A new function jpeg_mem_src() is ported from jpeg lib v8c to support
decode/encode in memory. The source code is coming from
(merge of Change-Id: I4d7f81fbb9a9e0cecaadd1855fc9f34296ba3eae)
http://www.ijg.org/files/jpegsrc.v8c.tar.gz

Change-Id: Ibbc86ae6d5d041b7018b640395f8c7399de76acb
VeNum optimizations

    jpeg-VeNum-optimization-of-IDCT-YCbCr-to-RGB-color-c

    Preserve registers D8-D15 when using VFP as specified by
    AAPCS v2.03

    Additionally had to split jdcolor-armv7.S into two files to
    resolve the issue of constants not being addressable in the
    code segment.

    Remove unused IDCT code

libjpeg: Remove unused idct VeNum references

Change-Id: Iec8433715768fc20b509cc016f76e4c4d816fde7

work-around bug in gcc binutils that causes linker errors when stripping obj code
(cherry picked from commit 02c7af886a156decdc230b18f929885e3051c900)