#12 Improve "const correctness"

[Markus Elfring]

Would you like to apply the advices from the article
"http://en.wikipedia.org/wiki/Const_correctness" to
your sources?
I suggest to add the key word "const" to the type
specifiers for parameters like the following.

http://cvs.sourceforge.net/viewcvs.py/html2fo/html2fo/html2fo.h?rev=1.16&view=markup
find, multi (function "strrecmulticmp")
s (function "isspacestr")
pParentTag, TagName (function "SearchTagType")