cmLocalVisualStudio7Generator: Rename local 'lang' var

In the WriteGroup method, rename the 'lang' var to 'ppLang' since
it is specifically for the preprocessor definitions language selection.
VS: Fix ASM_MASM support in VS >= 10

Fix a typo introduced by commit ce511435 (stringapi: Use strings for the
languages, 2014-02-03) to check the language name correctly.
VS: Move internal MasmEnabled member up to VS 7 generator

Move the member from cmGlobalVisualStudio10Generator to
cmGlobalVisualStudio7Generator to make it useful for earlier
versions of VS.  Set the member to true only starting with
cmGlobalVisualStudio8Generator since we will not implement
MASM support for versions less than VS 8.
VS: Add MASM support to VS 8 and 9 (#8170, #14984)
VS: Add test for MASM support

It is now expected to work with VS >= 8 and MSVC >= 13.0 for i386.
Merge topic 'vs-windows-sdk-desktop-arm'

2b20110f MSVC: Select default standard libraries for ARM platform
2dfcf0ed VS: Fix generation of desktop applications for ARM
dbb5a7ee CMakeDetermineCompilerId: Fix detection for VS ARM platform
Merge branch 'master' into next
Merge topic 'vs-masm' into next

962d179d VS: Add test for MASM support
19880cc5 VS: Add MASM support to VS 8 and 9 (#8170, #14984)
34729294 VS: Move internal MasmEnabled member up to VS 7 generator
a934a846 VS: Fix ASM_MASM support in VS >= 10
9ef7e086 cmLocalVisualStudio7Generator: Rename local 'lang' var