Make libQtCore a support library like boost and implement encoding conversion

Make libQtCore a support library like boost and implement encoding conversion
from/to the local 8bit encoding with it.
Only the autotools build system is updated, scons and cmake users need to
add qt4 cpp flags when compiling libsupport, and link libsupport against
libQtCore.

	* src/frontends/qt4/qt_helpers.[Ch]
	(toqstr, qchar_to_ucs4, ucs4_to_qchar, ucs4_to_qstring,
	 qstring_to_ucs4, fromqstr): Move these qstring conversion functions
	from here ...

	* src/support/qstring_helpers.[Ch] ... to these new files

	* src/support/docstring.[Ch]
	(from_local8bit): new conversion function from local 8bit encoding
	to ucs4
	(to_local8bit): new conversion function from ucs4 to local 8bit
	encoding to ucs4
	(to_local8bit_failure): exception that is thrown by to_local8bit if
	the argument cannot be converted to the local encoding

	* src/support/filename.C
	(FileName::toFilesystemEncoding): implement with the help of QFile

	* src/support/Makefile.am: Add new files, qt4 cpp flags and link
	against libQtCore

	* src/client/client.C: Convert commandline input from local encoding
	to ucs4. Convert stuff that is sent to to the server to utf8,
	because LyX interprets it as utf8 on the other end of the pipe.

	* src/lyx_main.C
	(LyX::exec): convert commandline input from local encoding to utf8
	(LyX::init): ditto
	(LyX::easyParse): ditto

	* development/scons/scons_manifest.py: Add new files

	* config/qt4.m4: Define new variables QT4_CORE_INCLUDES,
	QT4_CORE_LDFLAGS and QT4_CORE_LIB

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@16257 a592a061-630c-0410-9148-cb99ea01b6c8