Update README and documentation to mention OpenSSL dependency (#1322).

README.md

@@ -47,8 +47,9 @@ CMake is used for configuration management.
 
 The build depends on the following external libraries:
 
-- libreadline and libreadline-dev
-- GNU bfd (part of GNU binutils).
+- Readline development files (libreadline-dev/readline-devel package).
+- OpenSSL development files (libssl-dev/openssl-devel package).
+- GNU bfd which is the part of GNU binutils (binutils-dev/binutils-devel package).
 
 Please follow these steps to compile Tarantool:
 

doc/sphinx/dev_guide/building_from_source.rst

@@ -33,6 +33,7 @@ explain what the steps are, then on the Internet you can look at some example sc
    * **git**                                  # see above
    * **cmake**                                # see above
    * **libreadline-dev or libreadline6-dev or readline-devel**  # for interactive mode
+   * **libssl-dev**                           # for `digest` module
    * **autoconf**                             # optional, only in Mac OS scripts
    * **zlib1g** or **zlib**                   # optional, only in Mac OS scripts
    * **doxygen**                              # optional, only for documentation