Fix miscellaneous typos.

Found via `codespell -q 3`

m4/bswap.m4

@@ -36,7 +36,7 @@ dnl Dtermine whether the compiler has the __builtin_bswap32() intrinsic which
 dnl is likely to be present for most versions of GCC as well as Clang.
 
 AC_DEFUN([XIPH_C_BSWAP32],
-[AC_CACHE_CHECK(for bswap32 instrinsic,
+[AC_CACHE_CHECK(for bswap32 intrinsic,
   ac_cv_c_bswap32,
 
   # Initialize to no
@@ -63,7 +63,7 @@ dnl Dtermine whether the compiler has the __builtin_bswap16() intrinsic which
 dnl is likely to be present for most versions of GCC as well as Clang.
 
 AC_DEFUN([XIPH_C_BSWAP16],
-[AC_CACHE_CHECK(for bswap16 instrinsic,
+[AC_CACHE_CHECK(for bswap16 intrinsic,
   ac_cv_c_bswap16,
 
   # Initialize to no

m4/ogg.m4

@@ -101,7 +101,7 @@ int main ()
        echo "*** If you have an old version installed, it is best to remove it, although"
        echo "*** you may also be able to get things to work by modifying LD_LIBRARY_PATH"],
        [ echo "*** The test program failed to compile or link. See the file config.log for the"
-       echo "*** exact error that occured. This usually means Ogg was incorrectly installed"
+       echo "*** exact error that occurred. This usually means Ogg was incorrectly installed"
        echo "*** or that you have moved Ogg since it was installed." ])
        CFLAGS="$ac_save_CFLAGS"
        LIBS="$ac_save_LIBS"

m4/xmms.m4

@@ -127,7 +127,7 @@ else
             echo "*** being found. The easiest way to fix this is to remove the old version"
             echo "*** of XMMS, but you can also set the XMMS_CONFIG environment to point to the"
             echo "*** correct copy of xmms-config. (In this case, you will have to"
-            echo "*** modify your LD_LIBRARY_PATH enviroment variable, or edit /etc/ld.so.conf"
+            echo "*** modify your LD_LIBRARY_PATH environment variable, or edit /etc/ld.so.conf"
             echo "*** so that the correct libraries are found at run-time)"
 	fi
     fi