Revert of Remove the rtc_relative_path GYP variable and similar defines

Revert of Remove the rtc_relative_path GYP variable and similar defines (patchset #1 id:1 of https://codereview.webrtc.org/1903553003/ )

Reason for revert:
Breaks downstream for SRTP include paths. Will rework this and reland without that one.

Original issue's description:
> Remove the rtc_relative_path GYP variable and similar defines
>
> The defines that can be used to alter the include paths for Expat, SRTP
> and gtest are no longer needed in WebRTC or Chromium. Let's remove them
> to simplify the GYP a little.
>
> Removed defines:
> EXPAT_RELATIVE_PATH
> GTEST_RELATIVE_PATH
> SRTP_RELATIVE_PATH
>
> They're all set in the Chromium build so this shouldn't affect Chromium:
> https://code.google.com/p/chromium/codesearch#chromium/src/third_party/libjingle/libjingle.gyp
>
> BUG=webrtc:4256
> NOTRY=True
> NOPRESUBMIT=True
>
> Committed: https://crrev.com/e19cf59eb6ee44fd4d7e7fbcfdd1a6ea75063605
> Cr-Commit-Position: refs/heads/master@{#12467}

TBR=pthatcher@webrtc.org,perkj@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:4256
Committed: https://crrev.com/7bc7c06e6ad2663e7bd766308b9fbe2fb3514337
Cr-Commit-Position: refs/heads/master@{#12468}

[kjellander_webrtc, 2016-04-22 11:57:34]

Created Revert of Remove the rtc_relative_path GYP variable and similar defines

[commit-bot: I haz the power, 2016-04-22 11:57:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1913043003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1913043003/1

[commit-bot: I haz the power, 2016-04-22 11:57:53]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-04-22 11:58:03]

Description was changed from

==========
Revert of Remove the rtc_relative_path GYP variable and similar defines
(patchset #1 id:1 of https://codereview.webrtc.org/1903553003/ )

Reason for revert:
Breaks downstream for SRTP include paths. Will rework this and reland without
that one.

Original issue's description:
> Remove the rtc_relative_path GYP variable and similar defines
> 
> The defines that can be used to alter the include paths for Expat, SRTP
> and gtest are no longer needed in WebRTC or Chromium. Let's remove them
> to simplify the GYP a little.
> 
> Removed defines:
> EXPAT_RELATIVE_PATH
> GTEST_RELATIVE_PATH
> SRTP_RELATIVE_PATH
> 
> They're all set in the Chromium build so this shouldn't affect Chromium:
>
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/libjin...
> 
> BUG=webrtc:4256
> NOTRY=True
> NOPRESUBMIT=True
> 
> Committed: https://crrev.com/e19cf59eb6ee44fd4d7e7fbcfdd1a6ea75063605
> Cr-Commit-Position: refs/heads/master@{#12467}

TBR=pthatcher@webrtc.org,perkj@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:4256
==========

to

==========
Revert of Remove the rtc_relative_path GYP variable and similar defines
(patchset #1 id:1 of https://codereview.webrtc.org/1903553003/ )

Reason for revert:
Breaks downstream for SRTP include paths. Will rework this and reland without
that one.

Original issue's description:
> Remove the rtc_relative_path GYP variable and similar defines
>
> The defines that can be used to alter the include paths for Expat, SRTP
> and gtest are no longer needed in WebRTC or Chromium. Let's remove them
> to simplify the GYP a little.
>
> Removed defines:
> EXPAT_RELATIVE_PATH
> GTEST_RELATIVE_PATH
> SRTP_RELATIVE_PATH
>
> They're all set in the Chromium build so this shouldn't affect Chromium:
>
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/libjin...
>
> BUG=webrtc:4256
> NOTRY=True
> NOPRESUBMIT=True
>
> Committed: https://crrev.com/e19cf59eb6ee44fd4d7e7fbcfdd1a6ea75063605
> Cr-Commit-Position: refs/heads/master@{#12467}

TBR=pthatcher@webrtc.org,perkj@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:4256

Committed: https://crrev.com/7bc7c06e6ad2663e7bd766308b9fbe2fb3514337
Cr-Commit-Position: refs/heads/master@{#12468}
==========

[commit-bot: I haz the power, 2016-04-22 11:58:05]

Patchset 1 (id:??) landed as
https://crrev.com/7bc7c06e6ad2663e7bd766308b9fbe2fb3514337
Cr-Commit-Position: refs/heads/master@{#12468}