Reimplement isinf/isnan/fpclassify.

Also move isinf and isnan into libc like everyone else.

Also move fpclassify to libc like the BSDs (but unlike glibc). We need
this to be able to upgrade our float/double/long double parsing to gdtoa.

Also add some missing aliases. We now have all of:

  isnan, __isnan, isnanf, __isnanf, isnanl, __isnanl,
  isinf, __isinf, isinff, __isinff, isinfl, __isinfl,
  __fpclassify, __fpclassifyd, __fpclassifyf, __fpclassifyl.

Bug: 13469877
Change-Id: I407ffbac06c765a6c5fffda8106c37d7db04f27d

libm/Android.mk

@@ -1,10 +1,10 @@
 LOCAL_PATH:= $(call my-dir)
 
-# TODO: these come from from upstream's libc, not libm!
+# TODO: this comes from from upstream's libc, not libm, but it's an
+# implementation detail that should have hidden visibility, so it needs
+# to be in whatever library the math code is in.
 libm_common_src_files := \
     digittoint.c  \
-    fpclassify.c \
-    isinf.c  \
 
 # TODO: this is not in the BSDs.
 libm_common_src_files += \
@@ -129,7 +129,6 @@ libm_common_src_files += \
     upstream-freebsd/lib/msun/src/s_ilogb.c \
     upstream-freebsd/lib/msun/src/s_ilogbf.c \
     upstream-freebsd/lib/msun/src/s_isfinite.c \
-    upstream-freebsd/lib/msun/src/s_isnan.c \
     upstream-freebsd/lib/msun/src/s_isnormal.c \
     upstream-freebsd/lib/msun/src/s_llrint.c \
     upstream-freebsd/lib/msun/src/s_llrintf.c \
@@ -237,6 +236,7 @@ libm_common_cflags := \
     -include $(LOCAL_PATH)/freebsd-compat.h \
 
 libm_common_includes := $(LOCAL_PATH)/upstream-freebsd/lib/msun/src/
+
 libm_ld_includes := $(LOCAL_PATH)/upstream-freebsd/lib/msun/ld128/
 
 #