2011-06-21 ago some arrow symbols from DejaVuSansMono for bsub/esub/bsup/esup;
2011-06-20 ago removed obsolete font specification;
2011-06-19 ago abbreviations for special control symbols;
2011-06-19 ago some unicode chars for special control symbols;
2011-04-06 ago more symbol abbrevs;
2010-11-08 ago avoid clash of \<upharpoonright> vs. \<restriction> (cf. 666ea7e62384 and 3c49dbece0a8);
2010-05-31 ago tuned abbrevs for long arrows, according to usual ASCII syntax;
2009-10-29 ago removed slightly exotic symbol abbreviations for now -- achieves a coherent (unique) mapping;
2009-10-23 ago Fix a duplicate abbreviation || in etc/symbols.
2009-06-26 ago tuned abbrevs;
2009-06-23 ago fixed abbrev !! for \<And>;
2008-12-20 ago removed Ids;
2008-08-24 ago activated \<A>, \<a>, \<AA>, \<aa>;
2008-08-16 ago tuned abbrevs;
2008-08-15 ago added some abbrevs;
2008-08-15 ago removed redundant "symbol" property;
2008-08-15 ago Default interpretation of some Isabelle symbols.