Revert "Finally remove TFile::UseCache() which was marked for removal by v5-32-00."

This reverts commit 285a268e8149fdf3b211d307a2fd2a6baa28eebd.
It needs additional changes in roottest.
Add Error about invalid argument expression.
Remove unused variable.
Finally remove TFile::UseCache() which was marked for removal by v5-32-00.

Now roottest has been fixed too.
Indent Python examples.
Protection added in case of length=0 string in TMathText. Wrong PS was generated.
Compatibility with the TLatex greek characters
Some fixes from Christoph Deil
Fix a mistake in the more-log-labels option along Y
SQL documentation update. Fixes issue ROOT-5361.
Avoid unnecessary lookup in TMethodCall::GetMethod.
fix C++ syntax.
Fixed passing options in TWebFile.

By Costin.
Add newline; (some?) fwd decls do not have one.
Use initialization lists; that is what they are for (Coverity 52116)
Extract the CallFunc wrapper "by hand".
Fix passing object of class type by value.
Support function to function pointer decay in return value.
In ReturnSynthesizer add better support for RecordType.

When we dectect that the last expression is a record type and is not
a temporary, we now return it by reference, hence avoiding an unnecessary
and sometimes impossible (cout) copy.   If it is a temporary we still
return a 'copy'.
We must have a function implementation to take its address