feat(frontends/lean): display eval/check/find_decl results using flycheck
doc(syntax_highlight_in_latex.md): fix typo

[skip ci]
test(tests/lean/run): add test for well_founded relation for mutually recursive datatypes
fix(frontends/lean): disable class-instance resolution when executing find_decl, fixes #343
feat(kernel/expr): change the rules for inferring implicit arguments, closes #344
test(tests/lean/run): direct subterm for non-reflexive datatype
test(tests/lean/run): add another subterm example
feat(library/definitional/projection): use strict implicit inference, closes #344
fix(src/emacs/lean-flycheck): do not report 'sorry' warnings to flycheck, this is a temporary workaround since there is an overlap between flycheck and lean-mode type info
feat(script): add script for collecting standard library compilation times
fix(frontends/lean/elaborator): unsolved metavariables, fix #329
feat(library/tactic): add 'clear' tactic, closes #341
feat(library/tactic): add 'revert' tactic, closes #346
feat(emacs): add syntax-highlight for clear and revert tactics
feat(library/tactic): add 'clears' and 'reverts' variants
chore(lean-mode): remove 'annoying' abbreviations
refactor(library/tactic): cleanup 'revert' and 'clear' tactics
refactor(library/tactic): move 'get_unused_name' to goal
feat(library/rename): add notation for `rename`
refactor(library/tactic/intros_tactic): change approach for generating fresh names for nameless 'intros'