Demote Windows XP to no_std only

Modify the tier 3 non-ARM targets to show the standard library will no longer build for these and there is no work being done to change that.

src/doc/rustc/src/platform-support.md

@@ -139,7 +139,7 @@ target | std | notes
 `armv7r-none-eabi` | * | Bare ARMv7-R
 `armv7r-none-eabihf` | * | Bare ARMv7-R, hardfloat
 `asmjs-unknown-emscripten` | ✓ | asm.js via Emscripten
-`i586-pc-windows-msvc` | ✓ | 32-bit Windows w/o SSE
+`i586-pc-windows-msvc` | * | 32-bit Windows w/o SSE
 `i586-unknown-linux-gnu` | ✓ | 32-bit Linux w/o SSE (kernel 4.4, glibc 2.23)
 `i586-unknown-linux-musl` | ✓ | 32-bit Linux w/o SSE, MUSL
 `i686-linux-android` | ✓ | 32-bit x86 Android
@@ -236,7 +236,7 @@ target | std | host | notes
 `hexagon-unknown-linux-musl` | ? |  |
 `i386-apple-ios` | ✓ |  | 32-bit x86 iOS
 `i686-apple-darwin` | ✓ | ✓ | 32-bit macOS (10.7+, Lion+)
-`i686-pc-windows-msvc` | ✓ |  | 32-bit Windows XP support
+`i686-pc-windows-msvc` | * |  | 32-bit Windows XP support
 `i686-unknown-haiku` | ✓ | ✓ | 32-bit Haiku
 `i686-unknown-netbsd` | ✓ | ✓ | NetBSD/i386 with SSE2
 [`i686-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | 32-bit OpenBSD
@@ -283,7 +283,7 @@ target | std | host | notes
 [`wasm64-unknown-unknown`](platform-support/wasm64-unknown-unknown.md) | ? |  | WebAssembly
 `x86_64-apple-ios-macabi` | ✓ |  | Apple Catalyst on x86_64
 `x86_64-apple-tvos` | * | | x86 64-bit tvOS
-`x86_64-pc-windows-msvc` | ✓ |  | 64-bit Windows XP support
+`x86_64-pc-windows-msvc` | * |  | 64-bit Windows XP support
 `x86_64-sun-solaris` | ? |  | Deprecated target for 64-bit Solaris 10/11, illumos
 `x86_64-unknown-dragonfly` | ✓ | ✓ | 64-bit DragonFlyBSD
 `x86_64-unknown-haiku` | ✓ | ✓ | 64-bit Haiku