This patch adds support for an easier syntax for customizing which
version of Visual Studio msvs.py targets. It also allows users to
specify the PlatformToolset property on projects generated by waf. This
is necessary in order to properly generate projects for newer versions
of Visual Studio such as 2013 and 2015.
Example Syntax:
To generate a solution targeted at visual studio 2013 use the following
example:
```Python
class msvs_2013(msvs.msvs_generator):
cmd = 'msvs2013'
numver = '13.00'
vsver = '2013'
platform_toolset_ver = 'v120'
```
This will populate the associated fields correctly for msvs 2013.
With the addition of one new field, the project files generated by
the msvs command can be opened by 2012 as well as 2010.
Change-Id: I27c3a04ec156029f7a6690b27cf27013f5816d2f
Signed-off-by: Thomas Nagy <tnagy2pow10@gmail.com>