feat(kernel): add max_free_var function

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(frontends/lean): allow the user to set the trust_imported flag when creating environments using Lua

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
refactor(kernel/free_vars): replace max_free_var with relaxed free_var_range

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(util/debug): avoid infinite loop when Ctrl-D is pressed after an assertion violation

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(builtin/util): bug incorrect encoding of \t and \n in regular expression, and missing local

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(kernel/free_vars): make free_vars module functions more robust

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library): match procedure for higher-order patterns

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>