Minor fixes to README.txt file.

(cherry picked from commit b48b833dab)

README.txt

@@ -156,8 +156,9 @@ step. There may be dangling references, and it is not yet clear which
 module is the root.
 
 One can see a human readable version of the final pform by using the
-``-P <path>'' flag to the compiler. This will cause iverilog to dump
-the pform into the file named <path>.
+``-P <path>'' flag to the ``ivl'' subcommand. This will cause ivl
+to dump the pform into the file named <path>. (Note that this is not
+normally done, unless debugging the ``ivl'' subcommand.)
 
 3.3 Elaboration
 

StringHeap.h

@@ -38,7 +38,7 @@ class perm_string {
       operator const char* () const { return str(); }
 
 	// This is an escape for making perm_string objects out of
-	// literals. For example, per_string::literal("Label"); Please
+	// literals. For example, perm_string::literal("Label"); Please
 	// do *not* cheat and pass arbitrary const char* items here.
       static perm_string literal(const char*t) { return perm_string(t); }