#1 Improve const-correctness

[Markus Elfring]

Would you like to apply the advices from the article "http://en.wikipedia.org/wiki/Const-correctness" to more places in your sources?
I suggest to add the key word "const" to the type specifiers for parameters like the following.
- http://scsirastools.svn.sourceforge.net/viewvc/scsirastools/trunk/src/sgcommon.c?revision=2&view=markup
devtype_array, HeaderStr, rgascii (variables)
chp (function "itoh")
buffer, pattern (function "findmatch")

- http://scsirastools.svn.sourceforge.net/viewvc/scsirastools/trunk/src/sgdiskmon.c?revision=2&view=markup
dstat_str, vendor12 (global variables)
buf (function "showit")