[DOC] [Bug #19290] fix formatting

ext/objspace/objspace.c

@@ -954,7 +954,7 @@ void Init_objspace_dump(VALUE rb_mObjSpace);
  *
  * You need to <code>require 'objspace'</code> to use this extension module.
  *
- * Generally, you *SHOULD NOT* use this library if you do not know
+ * Generally, you *SHOULD* *NOT* use this library if you do not know
  * about the MRI implementation.  Mainly, this library is for (memory)
  * profiler developers and MRI developers who need to know about MRI
  * memory usage.

signal.c

@@ -1383,7 +1383,7 @@ reserved_signal_p(int signo)
  *     Signal.trap("CLD")  { puts "Child died" }
  *     fork && Process.wait
  *
- * produces:
+ * <em>produces:</em>
  *     Terminating: 27461
  *     Child died
  *     Terminating: 27460
@@ -1535,10 +1535,10 @@ int ruby_enable_coredump = 0;
  *     # ...
  *     Process.kill("TERM", pid)
  *
- * produces:
+ * <em>produces:</em>
  *     Debug now: true
  *     Debug now: false
- *    Terminating...
+ *     Terminating...
  *
  * The list of available signal names and their interpretation is
  * system dependent. Signal delivery semantics may also vary between

warning.rb

@@ -15,7 +15,7 @@ module Kernel
   #
   #    warn("warning 1", "warning 2")
   #
-  #  <em>produces:</em>
+  # <em>produces:</em>
   #
   #    warning 1
   #    warning 2
@@ -35,7 +35,7 @@ module Kernel
   #
   #    bar
   #
-  #  <em>produces:</em>
+  # <em>produces:</em>
   #
   #    baz.rb:6: warning: invalid call to foo
   #