Remove the -faltivec alias option and replace it with -maltivec everywhere.
The alias was only ever used on darwin and had some issues there,
and isn't used in practice much. Also fixes a problem with -mno-altivec
not turning off -maltivec.

Also add a diagnostic for faltivec/fno-altivec that directs users to use
maltivec options and include the altivec.h file explicitly.

llvm-svn: 298449
diff --git a/clang/docs/ClangCommandLineReference.rst b/clang/docs/ClangCommandLineReference.rst
index c7aead9..fb4c4a6 100644
--- a/clang/docs/ClangCommandLineReference.rst
+++ b/clang/docs/ClangCommandLineReference.rst
@@ -1053,7 +1053,7 @@
 
 .. option:: -fallow-unsupported
 
-.. option:: -faltivec, -fno-altivec, -maltivec
+.. option:: -maltivec, -mno-altivec
 
 Enable AltiVec vector initializer syntax