Spelling fixes in .txt files

ivlpp/ivlpp.txt

@@ -95,7 +95,7 @@ keys, with their corresponding values, are:
       This is exactly the same as the "-Dname=<value>" described above.
 
    I:<dir>
-      This is exctly the same as "-I<dir>".
+      This is exactly the same as "-I<dir>".
 
    relative include:<flag>
       The <flag> can be "true" or "false". This enables "relative

tgt-vvp/README.txt

@@ -3,7 +3,7 @@ THE VVP TARGET
 
 SYMBOL NAME CONVENTIONS
 
-There are some naming conventions that the vp target uses for
+There are some naming conventions that the vvp target uses for
 generating symbol names.
 
 * wires and regs

vvp/README.txt

@@ -535,8 +535,8 @@ implicit from these numbers. The <symbol> is then the input source.
 
 SUBSTITUTION STATEMENTS:
 
-The substition statement doesn't have a direct analog in Verilog, it
-only turns up in synthesis. It is a sorthand for forms like this:
+The substitution statement doesn't have a direct analog in Verilog, it
+only turns up in synthesis. It is a shorthand for forms like this:
 
    foo = <a>;
    foo[n] = <s>;

vvp/opcodes.txt

@@ -118,7 +118,7 @@ event control registers to determine when to perform the assign.
 %evctl is used to set the event control information.
 
 * %assign/v0 <var-label>, <delay>, <bit> (XXXX Old description)
-* %assign/v0/d <var-label>, <delayx>, <bit> (XXXX Old description
+* %assign/v0/d <var-label>, <delayx>, <bit> (XXXX Old description)
 * %assign/v0/e <var-label>, <bit> (XXXX Old description)
 
 The %assign/v0 instruction is a vector version of non-blocking
@@ -142,8 +142,8 @@ assignments. For blocking assignments, see %set/v.
 * %assign/vec4/d <var-label>, <delayx>
 * %assign/vec4/e <var-label>
 
-The %assign/vec4 instruction if a vec4 version of non-blocking
-assignment, The <delay> is the number lf clock ticks in the future
+The %assign/vec4 instruction is a vec4 version of non-blocking
+assignment. The <delay> is the number of clock ticks in the future
 where the assignment should schedule, and the value to assign is
 pulled from the vec4 stack.
 
@@ -536,7 +536,7 @@ part comes from the width of the popped value, and the <off> is an
 index register that contains the canonical offset where the value
 sets written.
 
-The %foce/vec4/off instruction will test the value if flags[4], and if
+The %force/vec4/off instruction will test the value of flags[4], and if
 it is 1, will suppress the actual assignment. This is intended to help
 with detection of invalid index expressions.