gitattributes: rename the c-style attribute

Since KWSys is meant to be imported into dependent projects, adding
`kwsys` to the attribute name should avoid conflicts with those set in
the parent project.

.gitattributes

@@ -3,8 +3,8 @@
 .gitattributes  -export-ignore
 .hooks*          export-ignore
 
-# Custom attribute to mark sources as using our C code style.
-[attr]our-c-style  whitespace=tab-in-indent  format.clang-format
+# Custom attribute to mark sources as using the kwsys C code style.
+[attr]kwsys-c-style  whitespace=tab-in-indent  format.clang-format
 
 /GitSetup        export-ignore
 /*.sh            export-ignore eol=lf
@@ -12,13 +12,13 @@
 /.clang-format   export-ignore
 # import on
 
-*.c              our-c-style
-*.c.in           our-c-style
-*.cxx            our-c-style
-*.h              our-c-style
-*.h.in           our-c-style
-*.hxx            our-c-style
-*.hxx.in         our-c-style
+*.c              kwsys-c-style
+*.c.in           kwsys-c-style
+*.cxx            kwsys-c-style
+*.h              kwsys-c-style
+*.h.in           kwsys-c-style
+*.hxx            kwsys-c-style
+*.hxx.in         kwsys-c-style
 
 *.cmake          whitespace=tab-in-indent
 *.rst            whitespace=tab-in-indent conflict-marker-size=79