UTF8 CHARACTERS IN PATH
PROBLEM AND FIX:
If the shared library name in INSTALL PLUGIN contains an
invalid UTF8 character, then it causes hang in the release
build and it raises an assert in the function my_strcspn
in debug builds.

The reason for this failure is because in macro SCAN_STRING,
my_mbcharlen returns zero if there is any invalid encoding
of the character which results in assertion being 
triggered in debug builds and in release build it gets into 
an infinite loop causing a hang. The client can supply an 
invalid utf8 encoded character and cause a hang of session,
the assert needs to be removed and fixed.

The fix is to return zero to the caller if my_mbcharlen
returns zero in SCAN_STRING. The function my_strchr has
also been modified to return NULL if it encounters an        
invalid UTF8 char while walking through the supplied
string. Also other uses of my_mbcharlen have been 
identified and error has been propagated.

NOTE:The 'CHARSET UTF8' needs to be executed prior to using 
utf8 in the windows OS at mysql client prompt to read utf8
encoded characters.