Get rid of WANT_FLOAT128 usage in floatn.h

This header is installed system-wide. It's not correct to introduce a new
macro WANT_FLOAT128 in this because then we are either forcing the compiler to
make it an inbuilt macro to make glibc expose all float128 functionality, or asking
our clients to -DWANT_FLOAT128 to get float128 functionality in glibc.

Given we are primarily going to have float128 enabled GRTE now, we don't need to have
guards for non-float128 cases.

Makefile

@@ -252,10 +252,6 @@ mostlyclean: parent-mostlyclean
 tests-clean:
 	@$(MAKE) subdir_testclean no_deps=t
 
-ifeq ($(enable-float128),yes)
-CPPFLAGS += -DWANT_FLOAT128=1
-endif
-
 ifneq (,$(CXX))
 vpath c++-types.data $(+sysdep_dirs)
 

math/Makefile

@@ -160,10 +160,6 @@ gen-calls = s_ldexpF
 generated += $(foreach s,.c .S,$(call type-foreach, $(calls:s_%=m_%$(s))))
 routines = $(call type-foreach, $(calls))
 
-ifeq ($(enable-float128),yes)
-math-CPPFLAGS += -DWANT_FLOAT128=1
-endif
-
 ifeq ($(build-mathvec),yes)
 # We need to install libm.so and libm.a as linker scripts
 # for transparent use of vector math library.

sysdeps/x86/bits/floatn.h

@@ -33,7 +33,7 @@
 #if (defined __x86_64__							\
      ? __GNUC_PREREQ (4, 3)						\
      : (defined __GNU__ ? __GNUC_PREREQ (4, 5) : __GNUC_PREREQ (4, 4))) \
-    || (defined __clang__ && defined WANT_FLOAT128 && WANT_FLOAT128 == 1)
+    || defined __clang__
 # define __HAVE_FLOAT128 1
 #else
 # define __HAVE_FLOAT128 0