add encode test for iOS
remove precompiled files
Use higher level APIs for getting the number of cores if WelsCPUFeatureDetect didn't report anything

On processors without HTT, WelsCPUFeatureDetect can't return
a number of cores but might still return a nonzero set of
CPU feature flags. Previously the nonzero cpu feature flag
indicated that cpuid worked and the encoder wouldn't use the
higher level API for getting the number of cores, even though the
number of cores was left at 1.
remove boilerplate comments
make the makefile is indepent with the pch file
Merge pull request #361 from mstorsjo/get-core-count

Use higher level APIs for getting the number of cores if WelsCPUFeatureDetect didn't report anything
Merge pull request #358 from volvet/add_ios_encDemo

add encode test for iOS
refine rpl
refine encode plus code
Merge pull request #366 from licaiguo/refine-rpl-pr

refine rpl
Merge pull request #367 from volvet/refine-enc-plus

refine encode plus code
refine welsEncoderEncodeExt
update comments on welsEncoderEncodeExt
Merge pull request #370 from volvet/develop_b

refine welsEncoderEncodeExt