Update release note

release_notes/RELEASE.txt

@@ -58,20 +58,19 @@ New features and changes
       volumes on MacOS 9 and earlier (publication CMU-CS-98-145 can be
       found via an internet search).
 
-      HDF4 allows a library builder to manually hard-code the FILELIB symbol
+      HDF4 allows a library builder to manually specify the FILELIB symbol
       found in hdfi.h to use C standard library buffered I/O (fopen, etc.),
       POSIX unbuffered I/O (open, etc.), or MacFS I/O (mopen, etc.). The
-      library default is to use C buffered I/O and there is no build-time
-      or run-time option to change that. Only manual editing is possible.
-      The FILELIB value is then used to map HI_OPEN, etc. to appropriate
-      I/O calls.
+      library default is to use C buffered I/O and there is no obvious
+      build-time or run-time option to change that. The FILELIB value is
+      then used to map HI_OPEN, etc. to appropriate I/O calls.
 
-      The "altnernative" I/O schemes (POSIX unbuffered and MacFS) are not
+      The "alternative" I/O schemes (POSIX unbuffered and MacFS) are not
       tested. Due to its age and obscurity, MacFS support is being dropped.
       The POSIX unbuffered I/O scheme will remain in place for now since it
       might be interesting to profile that vs C stdio.h calls.
 
-      This change will have NO IMPACT on modern Macs. Files created using
+      This change will have *NO IMPACT* on modern Macs. Files created using
       MacFS in the 90s and early 2000s can be accessed using C stanadard
       library I/O.