Issue #27076: Doc, comment and tests spelling fixes

Most fixes to Doc/ and Lib/ directories by Ville Skyttä.
diff --git a/configure b/configure
index 1823d14..3216ad7 100755
--- a/configure
+++ b/configure
@@ -3496,7 +3496,7 @@
 #
 # SGI compilers allow the specification of the both the ABI and the
 # ISA on the command line.  Depending on the values of these switches,
-# different and often incompatable code will be generated.
+# different and often incompatible code will be generated.
 #
 # The SGI_ABI variable can be used to modify the CC and LDFLAGS and
 # thus supply support for various ABI/ISA combinations.  The MACHDEP