Typo fixes

Doc/lib/libstdtypes.tex

@@ -728,7 +728,7 @@ a prefix; rather, all combinations of its values are stripped:
 \end{methoddesc}
 
 \begin{methoddesc}[string]{partition}{sep}
-Splits the string at the first occurence of \var{sep}, and return
+Split the string at the first occurrence of \var{sep}, and return
 a 3-tuple containing the part before the separator, the separator
 itself, and the part after the separator.  If the separator is not
 found, return a 3-tuple containing the string itself, followed by