configure: check for perl

Though not (currently) required this tests for perl in all
configurations.

Fixes issue #671

Change-Id: Ibe1e72db74bb4cf3252b73c68ff1dfc2ecfc902b
build: convert rtcd.sh to perl

significantly speeds up file generation.

the goal of this change is to convert rtcd.sh to perl as directly as
possible to allow for simple comparison. future changes can make it more
perl-like.

---
Linux
    [CREATE] vpx_scale_rtcd.h
real    0m0.485s ->    0m0.022s
    [CREATE] vp8_rtcd.h
real    0m4.619s ->    0m0.060s
    [CREATE] vp9_rtcd.h
real    0m10.102s ->    0m0.087s

Windows
    [CREATE] vpx_scale_rtcd.h
real    0m8.360s ->    0m0.080s
    [CREATE] vp8_rtcd.h
real    1m8.083s ->    0m0.160s
    [CREATE] vp9_rtcd.h
real    2m6.489s ->    0m0.233s

Change-Id: Idfb71188206c91237d6a3c3a81dfe00d103f11ee
vp8_decrypt_test.c: Silence MSVC data loss warning.

- Change type of encrypt_buffer() offset argument to ptrdiff_t, and change the
  type of the size argument to size_t.
- Update size argument encrypt_buffer() in vp8_boolcoder_test.c with
  same.

Change-Id: Ie29c7c82c73318bee01b89c6fb4c4e1442eef03c
nestegg: ne_read_(string|binary|block): normalize size_t usage

+ nestegg_track_codec_data
quiets uint64_t -> size_t warnings
the sizes used are previously validated against their associated LIMIT_*
values

Change-Id: Ie574a3a7496d0143bd58b778145c27f38dd6a4da
nestegg: ne_parse: normalize size_t usage

in calls to ne_read_simple / ne_io_read_skip

Change-Id: I5c4fc3bb41832973830ad54248839d6a4944aae6
nestegg: quiet read related uint64->size_t warnings

ne_read_ebml_lacing / ne_read_discard_padding
+ add some asserts

Change-Id: I28d0ec5c8f901ae0a35928a8f512c51b3ecf177d
nestegg: ne_buffer_read: quiet uint64->size_t warning

the buffer length is already a size_t making the offset into it limited

Change-Id: Ibc5352e69049186cc07f7d86117696b11a98a600
Avoid gf/altref boost in pick_q under svc cbr mode.

Change-Id: Ib719a9f74924718715592e0238bc391ae239d026
Merge "vp8_decrypt_test.c: Silence MSVC data loss warning."
msvs: filter out include-only asm files

avoid building x86inc.asm, x86_abi_support.asm and vpx_config.asm as
they provide no symbols themselves

fixes:
 warning LNK4221: This object file does not define any previously
undefined public symbols, so it will not be used by any link operation
that consumes this library

Change-Id: Iecfe03aa76efbfc07c2af5b91ba5405634e45f1d
Merge changes Ibc5352e6,I28d0ec5c,I5c4fc3bb,Ie574a3a7

* changes:
  nestegg: ne_buffer_read: quiet uint64->size_t warning
  nestegg: quiet read related uint64->size_t warnings
  nestegg: ne_parse: normalize size_t usage
  nestegg: ne_read_(string|binary|block): normalize size_t usage
Merge "msvs: filter out include-only asm files"
Merge changes Idfb71188,Ibe1e72db

* changes:
  build: convert rtcd.sh to perl
  configure: check for perl