Provide build deps for Alpine and CentOS

Provide build deps for Alpine and CentOS

Also updates build deps for Fedora and Debian,
and format the shell commands nicely.

See: https://github.com/pyldap/pyldap/issues/91#issuecomment-350098897

https://github.com/python-ldap/python-ldap/pull/113
Some changes by Petr Viktorin
Signed-off-by: Christian Heimes <cheimes@redhat.com>

Doc/installing.rst

@@ -1,3 +1,5 @@
+.. highlight:: console
+
 .. _installing:
 
 Installing python-ldap
@@ -18,7 +20,7 @@ The preferred point for downloading the “official” source distribution
 is the `PyPI repository`_ which supports installing via `pip`_.
 For example::
 
-    python -m pip install python-ldap
+    $ python -m pip install python-ldap
 
 .. _PyPI repository: https://pypi.python.org/pypi/python-ldap/
 .. _pip: https://pip.pypa.io/en/stable/
@@ -83,8 +85,8 @@ Mac OS X
 
 You can install directly with pip::
 
-    xcode-select --install
-    pip install python-ldap \
+    $ xcode-select --install
+    $ pip install python-ldap \
         --global-option=build_ext \
         --global-option="-I$(xcrun --show-sdk-path)/usr/include/sasl"
 
@@ -98,8 +100,8 @@ Installing from Source
 python-ldap is built and installed using the Python setuptools.
 From a source repository::
 
-    python -m pip install setuptools
-    python setup.py install
+    $ python -m pip install setuptools
+    $ python setup.py install
 
 If you have more than one Python interpreter installed locally, you should
 use the same one you plan to use python-ldap with.
@@ -132,22 +134,38 @@ on the local system when building python-ldap:
 .. _Cyrus SASL: https://www.cyrusimap.org/sasl/
 
 
+Alpine
+------
+
+Packages for building::
+
+    # apk add build-base openldap-dev python2-dev python3-dev
+
+CentOS
+------
+
+Packages for building::
+
+   # yum groupinstall "Development tools"
+   # yum install openldap-devel python-devel
+
 Debian
 ------
 
 Packages for building and testing::
 
-    apt-get install build-essential python3-dev python2.7-dev libldap2-dev \
-        libsasl2-dev slapd ldap-utils python-tox valgrind
-
+   # apt-get install build-essential python3-dev python2.7-dev \
+       libldap2-dev libsasl2-dev slapd ldap-utils python-tox \
+       lcov valgrind
 
 Fedora
 ------
 
 Packages for building and testing::
 
-    dnf install "@C Development Tools and Libraries" openldap-devel \
-        python2-devel python3-devel python3-tox valgrind clang-analyzer
+   # dnf install "@C Development Tools and Libraries" openldap-devel \
+       python2-devel python3-devel python3-tox \
+       lcov clang-analyzer valgrind
 
 .. note::