add uclibc support
* some variables defined with "char *" should be modified to "const char*"
* For uclibc, glibc's "void malloc_stats(void)" should be "void malloc_stats(FILE *)", is commented now.
* For uclibc, __sbrk is with attribute "hidden", so we use mmap allocator for uclibc.
add "-finstrument-functions" support for MIPS uclibc.
should configure with CXXFLAGS="-finstrument-functions"