Mark the stack as non-executable in the arm assembly

Otherwise the linker is forced to enable an executable stack for
executables that the code is linked into.
Merge pull request #473 from mstorsjo/arm-non-executable-stack

Mark the stack as non-executable in the arm assembly
3Author: ruil2 <ruil2@cisco.com>
 modify the parameter verification for SM_AUTO_SLICE mode -- uiSliceNum
 iis ignored
fix encode crash
Merge pull request #478 from volvet/fix-encode-crash

fix encode crash
fix double free crash in encoder
Merge pull request #479 from volvet/fix-double-free-crash

fix double free crash in encoder
Merge pull request #476 from ruil2/encoder_slice_auto

modify the parameter verification for SM_AUTO_SLICE mode, review at: https://rbcommons.com/s/OpenH264/r/184/
fix idr interval issue
Make arm assembly labels always start from the beginning of the line

A few labels were misformatted.
Merge pull request #481 from mstorsjo/arm-asm-labels

Make arm assembly labels always start from the beginning of the line
Merge pull request #480 from volvet/fix-idr-interval-issue

fix idr interval issue
Merge remote-tracking branch 'upstream/master' into travis.android