bug 490467: Renamed |SHA| symbol names on |sha2| module

this change is for resolving |sha2| symbol-conflict in using
|tinydtls| with other crypto modules. this symbol-conflict could
occur on the |tinydtls|-deployed systems with using |OpenSSL| or
|OpenSSL|-like, which has another |SHA| symbols.
In case of |iotivity-tinydtls|, the conflict occurs between
|iotivity-tinydtls| and the deployed |crypto| library, which has
also another |SHA|.

[patch #1] initial commit
[patch #2-3] updated commit message
[patch #4] reverted renaming for internal symbols
[patch #5] updated symbols with lower-case
[patch #6] fixed typo for calling API

bugs: https://bugs.eclipse.org/bugs/show_bug.cgi?id=490467

Change-Id: I6942870c7c31544e89a20209d21730406ffb08d2
Signed-off-by: Kyungsun Cho <goodsun.cho@samsung.com>
6 files changed