Various terminfo parameterization changes
Tweak new terminfo logical operator support
Tweak terminfo::parm::expand function signature

Take a new struct Variables instead of two &mut [] vectors for static
and dynamic variables.
Don't require &mut [Param] with terminfo::parm::expand()
Fix a bunch of failure cases in terminfo

Replace all potentially-failing operations with Err returns and add
tests.

Remove the Char parameter type; characters are represented as Numbers.

Fix integer constants to work properly when there are multiple constants
in the same capability string.

Tweak loop to use iterators instead of indexing into cap.
Implement terminfo param conditionals

Implement the %?, %t, %e, and %; operators. Also implement the %<, %=,
%> operators, without which conditionals aren't very useful.

Fix the order of parameters for the arithmetic operators.

Implement the missing %^ operator.
Fix line lengths in terminfo
auto merge of #7133 : kballard/rust/terminfo-parm, r=thestinger

Implement conditional support in terminfo, along with a few other related operators.

Fix implementation of non-commutative arithmetic operators.

Remove all known cases of task failure from `terminfo::parm::expand`, and change the method signature.

Fix some other miscellaneous issues.