Fix typos

Author: Felicity Chapman

cpp/ql/src/Critical/GlobalUseBeforeInit.ql

@@ -1,6 +1,6 @@
 /**
  * @name Global variable may be used before initialization
- * @description Using an uninitialized variable leads to undefined results.
+ * @description Using an uninitialized variable may lead to undefined results.
  * @kind problem
  * @id cpp/global-use-before-init
  * @problem.severity warning

cpp/ql/src/Critical/InconsistentNullnessTesting.qhelp

@@ -22,7 +22,7 @@ important system data (including the interrupt table in some architectures).
 <example>
 This code shows two examples where a pointer is dereferenced. 
 The first example checks that the pointer is not null before dereferencing it. 
-The second example fails to perform a nullnes check, leading to a potential vulnerability in the code.
+The second example fails to perform a nullness check, leading to a potential vulnerability in the code.
 <sample src="InconsistentNullnessTesting.cpp" />
 </example>
 

cpp/ql/src/Critical/OverflowCalculated.qhelp

@@ -30,7 +30,7 @@ Increase the size of the buffer being allocated.
 </recommendation>
 
 <example>
-<p>This example includes thre annotated calls that copy a string into a buffer.
+<p>This example includes three annotated calls that copy a string into a buffer.
 The first call to <code>malloc</code> creates a buffer that's the 
 same size as the string, leaving no space for the zero terminator 
 and causing an overflow. The second call to <ocde>malloc</code>