before overwriting it with a default value for oss-fuzz

A malformed tag like <foo could cause espeak to read past
the end of the string.

instead of current working directory
so, the fuzzer can be launched from anywhere

- fix a buffer overflow in ucd_tolower leading to failure when
compiling with address sanitizer
- force the use of C++ compiler for espeak-ng
- adding a malloc to have a null-terminated string in the fuzz target
- setting (but not overwriting) ESPEAK_DATA_PATH environment
variable inside the fuzz target

When set in a language file, a period followed by a lower case letter is
detected as end of sentence. Normal behavior is to require a capital
letter.

SSML logic has a bug (#410) where speech parameters are not changed when there's a
sentence elogic nd. The prosody bug test should fail.

This is intended for testing command line options such as -k 2, --punct
and so on.

The file is intended for everything mentioned in docs/dictionary.md.

This test is related to the next two lojban commits. Thanks to xunsku @ irc.freenode.org