minor updates on manual (#20258)

* minor updates on manual

1. statement -> keyword:

1. re-phase on the explanation of `import except`: maybe the newer version does not export some of the identifiers;

1. "The original module name is then not accessible" is moved up to the previous paragraph, since it is coupled with 
   the previous paragraph, but not the current one.

1. re-phase on the explanation of _Disabling certain messages_.

* Apply suggestions from code review

Co-authored-by: konsumlamm <44230978+konsumlamm@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Clay Sweetser <Varriount@users.noreply.github.com>

* Update manual.md

do not use "()".

* Update doc/manual.md

Co-authored-by: Clay Sweetser <Varriount@users.noreply.github.com>

Co-authored-by: konsumlamm <44230978+konsumlamm@users.noreply.github.com>
Co-authored-by: ringabout <43030857+ringabout@users.noreply.github.com>
Co-authored-by: Clay Sweetser <Varriount@users.noreply.github.com>

doc/manual.md

@@ -6499,7 +6499,7 @@ This is best illustrated by an example:
 Import statement
 ----------------
 
-After the `import` statement, a list of module names can follow or a single
+After the `import` keyword, a list of module names can follow or a single
 module name followed by an `except` list to prevent some symbols from being
 imported:
 
@@ -6512,8 +6512,8 @@ imported:
 
 
 It is not checked that the `except` list is really exported from the module.
-This feature allows us to compile against an older version of the module that
+This feature allows us to compile against different versions of the module,
-does not export these identifiers.
+even when one version does not export some of these identifiers.
 
 The `import` statement is only allowed at the top level.
 
@@ -6548,7 +6548,8 @@ The `include` statement can be used outside the top level, as such:
 Module names in imports
 -----------------------
 
-A module alias can be introduced via the `as` keyword:
+A module alias can be introduced via the `as` keyword, after which the original module name
+is inaccessible:
 
   ```nim
   import std/strutils as su, std/sequtils as qu
@@ -6556,8 +6557,7 @@ A module alias can be introduced via the `as` keyword:
   echo su.format("$1", "lalelu")
   ```
 
-The original module name is then not accessible. The notations
+The notations `path/to/module` or `"path/to/module"` can be used to refer to a module
-`path/to/module` or `"path/to/module"` can be used to refer to a module
 in subdirectories:
 
   ```nim
@@ -6614,7 +6614,7 @@ It is recommended and preferred but not currently enforced that all stdlib modul
 From import statement
 ---------------------
 
-After the `from` statement, a module name followed by
+After the `from` keyword, a module name followed by
 an `import` to list the symbols one likes to use without explicit
 full qualification:
 
@@ -7175,8 +7175,9 @@ Disabling certain messages
 --------------------------
 Nim generates some warnings and hints ("line too long") that may annoy the
 user. A mechanism for disabling certain messages is provided: Each hint
-and warning message contains a symbol in brackets. This is the message's
+and warning message is associated with a symbol. This is the message's
-identifier that can be used to enable or disable it:
+identifier, which can be used to enable or disable the message by putting it
+in brackets following the pragma:
 
   ```Nim
   {.hint[LineTooLong]: off.} # turn off the hint about too long lines