Clean up formatting of configure output for ARM intrinsics detection.

This makes it match the formatting of the output for ARM assembly
better, and removes some redundant repetition of the word
"intrinsics".  It also fixes the output if a compiler supports RTCD
for Neon intrinsics but not assembly.

Signed-off-by: Timothy B. Terriberry <tterribe@xiph.org>

configure.ac

@@ -485,10 +485,12 @@ AS_IF([test x"$enable_intrinsics" = x"yes"],[
       AS_IF([test x"$OPUS_ARM_MAY_HAVE_NEON_INTR" = x"1"],
       [
          AC_DEFINE([OPUS_ARM_MAY_HAVE_NEON_INTR], 1, [Compiler supports ARMv7/Aarch64 Neon Intrinsics])
-         intrinsics_support="$intrinsics_support (Neon_Intrinsics)"
+         intrinsics_support="$intrinsics_support (NEON)"
 
-         AS_IF([test x"enable_rtcd" != x"" && test x"$OPUS_ARM_PRESUME_NEON_INTR" != x"1"],
-            [rtcd_support="$rtcd_support (Neon_Intrinsics)"])
+         AS_IF([test x"$enable_rtcd" != x"no" && test x"$OPUS_ARM_PRESUME_NEON_INTR" != x"1"],
+            [AS_IF([test x"$rtcd_support" = x"no"],
+               [rtcd_support="ARM (NEON Intrinsics)"],
+               [rtcd_support="$rtcd_support (NEON Intrinsics)"])])
 
          AS_IF([test x"$OPUS_ARM_PRESUME_NEON_INTR" = x"1"],
             [AC_DEFINE([OPUS_ARM_PRESUME_NEON_INTR], 1, [Define if binary requires NEON intrinsics support])])
@@ -502,12 +504,9 @@ AS_IF([test x"$enable_intrinsics" = x"yes"],[
                  [rtcd_support="$rtcd_support (NE10)"])
          ])
 
-         AS_IF([test x"$rtcd_support" = x""],
-            [rtcd_support=no])
-
          AS_IF([test x"$intrinsics_support" = x""],
             [intrinsics_support=no],
-            [intrinsics_support="arm$intrinsics_support"])
+            [intrinsics_support="ARM$intrinsics_support"])
       ],
       [
          AC_MSG_WARN([Compiler does not support ARM intrinsics])