Make fnstcw work with emscripten

[Diomidis Spinellis]

When glibc is compiled with emscripten toolchain for compiling to asm.js 
and WebAssembly [1] (e.g. as part of groff), the compilation fails due 
to the inclusion of assembly code, as shown in the example below.

emcc groff.bc -o groff.html
In function vasnprintf()
void (i16*)* asm sideeffect "fnstcw $0", "=*m"
LLVM ERROR: asm() with non-empty content not supported, use EM_ASM() 
(see emscripten.h)

The following small change corrects this problem.

--- a/lib/fpucw.h  2019-10-12 15:27:25.810899880 +0300
+++ b/lib/fpucw.h 2019-10-12 14:25:30.875463263 +0300
@@ -62,7 +62,7 @@
  */

 /* Inline assembler like this works only with GNU C.  */
-#if (defined __i386__ || defined __x86_64__) && defined __GNUC__
+#if (defined __i386__ || defined __x86_64__) && defined __GNUC__ && 
!defined __EMSCRIPTEN__

 typedef unsigned short fpucw_t; /* glibc calls this fpu_control_t */


[1] https://emscripten.org/