[FIX] requirements: update for windows compatibility

problem: installing from the source on windows includes manual modification of the requiremnets, as well as
not supported package versions

solution:
- increased the version of lxml, werkzeug and pillow to the latest supported version in debian, it
will fix already a number of issues on windows
- automatically include or exclude dependencies from requirement.txt using requirement specifiers

Note that for lxml on windows, we will always install the latest version because the version 3.7.1 does not exist on
windows in WHL.

doc/setup/install.rst

@@ -360,13 +360,6 @@ Source installation requires manually installing dependencies:
     Install ``psycopg`` using the installer here
     http://www.stickpeople.com/projects/python/win-psycopg/
 
-    Then edit the requirements.txt file:
-
-    - remove ``psycopg2`` as you already have it.
-    - remove the optional ``python-ldap``, ``gevent`` and ``psutil`` because
-      they require compilation.
-    - add ``pypiwin32`` because it's needed under windows.
-
     Then use pip to install the dependencies using the following
     command from a cmd.exe prompt (replace ``\YourOdooPath`` by the actual
     path where you downloaded Odoo):

requirements.txt

@@ -3,22 +3,23 @@ decorator==4.0.10
 docutils==0.12
 ebaysdk==2.1.5
 feedparser==5.2.1
-gevent==1.1.2
+gevent==1.1.2 ; sys_platform != 'win32'
 greenlet==0.4.10
 html2text==2016.9.19
 Jinja2==2.8
-lxml==3.5.0
+lxml==3.7.1 ; sys_platform != 'win32'
+lxml ; sys_platform == 'win32'
 Mako==1.0.4
 MarkupSafe==0.23
 mock==2.0.0
 num2words==0.5.4
 ofxparse==0.16
 passlib==1.6.5
-Pillow==3.4.1
-psutil==4.3.1
-psycopg2==2.7.3.1
+Pillow==4.0.0
+psutil==4.3.1; sys_platform != 'win32'
+psycopg2==2.7.3.1; sys_platform != 'win32'
 pydot==1.2.3
-pyldap==2.4.28
+pyldap==2.4.28; sys_platform != 'win32'
 pyparsing==2.1.10
 PyPDF2==1.26.0
 pyserial==3.1.1
@@ -29,11 +30,11 @@ PyYAML==3.12
 qrcode==5.3
 reportlab==3.3.0
 requests==2.11.1
-six==1.10.0
 suds-jurko==0.6
 vatnumber==1.2
 vobject==0.9.3
-Werkzeug==0.11.11
+Werkzeug==0.11.15
 XlsxWriter==0.9.3
 xlwt==1.3.*
 xlrd==1.0.0
+pypiwin32 ; sys_platform == 'win32'