problem #1: udf_example.so does not get built on AIX

solution#1: build it yourself using
cd sql; gcc  -g -I ../include/ -I /usr/include/ -lpthread  \
-shared -o udf_example.so udf_example.c; mv udf_example.so \
.libs/ 

problem#2 (the bug): udf_example fails because it does not
recognize the variable LD_LIBRARY_PATH when doing dl_open(),
it looks at LIBPATH

solution#2: add the library path to LIBPATH

problem#3: udf_example returns the wrong result length since 
it relies on strmov to return a pointer to the end of the 
string that it copies. On AIX builds, where m_string.h is not
included (m_string defines a macro expanding strmov to stpcpy),
there is a macro expanding strmov to strcpy, which returns a 
pointer to the first character.

solution#3: define strmov as stpcpy.

problem#4: #2 applies on hp-ux as well, but this platform
looks at SHLIB_PATH

solution#4: added the library path to SHLIB_PATH