refine checks in ParseSps
finish syntax checks in ParseSps
update according to review comments
Merge pull request #335 from licaiguo/decoder-syntax-checks

Decoder syntax checks
cleanup encoder parameters
minor update
remove inter spatial layer prediction in parameters
Merge pull request #341 from ruil2/cleanup

cleanup encoder parameters--- review request #108
Merge pull request #342 from volvet/rm-unsupported-para

remove inter spatial layer prediction in parameters
cast to uint32_t in GET_WORD to prevent possible left shift error.
Merge pull request #343 from huili2/cast_get_word

cast to uint32_t in GET_WORD to prevent possible left shift error.
refine level check
Merge pull request #344 from licaiguo/fix-level-check

refine level check
fix int conversion warning, using LD32/ST32
use active SPS parameters instead of other SPS.
Merge pull request #345 from licaiguo/fix-int-conversion-warning

fix int conversion warning, using LD32/ST32
Merge pull request #347 from huili2/active_sps_ref_size

use active SPS parameters instead of other SPS.
Use -dynamiclib instead of -shared for building shared libraries on OS X

Older toolchains don't recognize the -shared parameter.
Add the necessary directories to the include path within xcode

This is not necessary when using precompiled headers.
Remove unnecessary precompiled headers

This reduces the huge amount of near-useless small extra files
scattered around for the sake of the platform demo projects.

This requires explicitly listing all the ncessary include paths.