Add a couple of useful string functions. (DO NOT MERGE)

            // start, or -1 if not found

            ssize_t             find(const char* other, size_t start = 0) const;

            // return true if this string contains the specified substring

    inline  bool                contains(const char* other) const;

            // removes all occurrence of the specified substring

            // returns true if any were found and removed

            bool                removeAll(const char* other);

            void                toLower();

            void                toLower(size_t start, size_t numChars);

            void                toUpper();

            void                toUpper(size_t start, size_t numChars);

    /*

     * These methods operate on the string as if it were a path name.

     */

    return SharedBuffer::bufferFromData(mString);

}

inline bool String8::contains(const char* other) const

{

    return find(other) >= 0;

}

inline String8& String8::operator=(const String8& other)

{

    setTo(other);

    return p ? p-mString : -1;

}

bool String8::removeAll(const char* other) {

    ssize_t index = find(other);

    if (index < 0) return false;

    char* buf = lockBuffer(size());

    if (!buf) return false; // out of memory

    size_t skip = strlen(other);

    size_t len = size();

    size_t tail = index;

    while (size_t(index) < len) {

        ssize_t next = find(other, index + skip);

        if (next < 0) {

            next = len;

        }

        memcpy(buf + tail, buf + index + skip, next - index - skip);

        tail += next - index - skip;

        index = next;

    }

    unlockBuffer(tail);

    return true;

}

void String8::toLower()

{

    toLower(0, size());