Fixed conversion from empty String to ByteVector
Also build/install taglib.pc when targetting windows

.pc file is notably used when cross-compiling windows software
Remove a superfluos 'x'
Merge pull request #340 from mineo/patch-1

Remove a superfluos 'x'
Use std::string::c_str() rather than &s[0] where a const pointer is required.
Avoid using &d->data[0] when d->data is empty.
Merge pull request #330 from TsudaKageyu/fix-emptystring

Fixed a bug reported at #328
Changed XM::File::save() to use seek() properly.
Merge pull request #347 from TsudaKageyu/xm-seek

Changed XM::File::save() to use seek() properly.
Reduced a useless memory copy in tstring.cpp.
Fixed a typo in INSTALL.
Merge pull request #349 from TsudaKageyu/install-typo

Fixed a typo in INSTALL.
Merge pull request #348 from TsudaKageyu/string-memcpy

Reduced a useless memory copy in tstring.cpp.
Merge pull request #338 from funman/master

Also build/install taglib_c.pc when targetting windows
Avoid using sprintf() in tagreader.cpp to fix an MSVC warning.
Merge pull request #352 from TsudaKageyu/tagreader-sprintf

Avoid using sprintf() in tagreader.cpp to fix an MSVC warning.
opus: Estimate the bitrate if possible
Merge pull request #354 from TsudaKageyu/opus-bitrate

opus: Estimate the bitrate if possible