Add "ctxt" and TyCtxt to the glossary (#937)

Author: camelid

src/appendix/glossary.md

@@ -13,6 +13,7 @@ completeness <div id="completeness"/>    |  A technical term in type theory, it
 control-flow graph <div id="cfg"/>       |  A representation of the control-flow of a program; see [the background chapter for more](./background.html#cfg)
 CTFE <div id="ctfe"/>                    |  Short for Compile-Time Function Evaluation, this is the ability of the compiler to evaluate `const fn`s at compile time. This is part of the compiler's constant evaluation system. ([see more](../const-eval.html))
 cx <div id="cx"/>                        |  We tend to use "cx" as an abbreviation for context. See also `tcx`, `infcx`, etc.
+ctxt <div id="ctxt"/>                    |  We also use "ctxt" as an abbreviation for context, e.g. [`TyCtxt`](TyCtxt). See also [cx](#cx) or [tcx](#tcx).
 DAG <div id="dag"/>                      |  A directed acyclic graph is used during compilation to keep track of dependencies between queries. ([see more](../queries/incremental-compilation.html))
 data-flow analysis <div id="data-flow"/> |  A static analysis that figures out what properties are true at each point in the control-flow of a program; see [the background chapter for more](./background.html#dataflow).
 DeBruijn Index <div id="debruijn">       |  A technique for describing which binder a variable is bound by using only integers. It has the benefit that it is invariant under variable renaming. ([see more](./background.md#what-is-a-debruijn-index))
@@ -73,7 +74,8 @@ span <div id="span"/>                    |  A location in the user's source code
 substs <div id="substs"/>                |  The substitutions for a given generic type or item (e.g. the `i32`, `u32` in `HashMap<i32, u32>`).
 Tag <div id="tag"/>                      |  The "tag" of an enum/generator encodes the [discriminant](#discriminant) of the active variant/state.  Tags can either be "direct" (simply storing the discriminant in a field) or use a ["niche"](#niche).
 tcx <div id="tcx"/>                      |  The "typing context", main data structure of the compiler. ([see more](../ty.html))
-'tcx <div id="lifetime-tcx"/>            |  The lifetime of the allocation arena. ([see more](../ty.html))
+`'tcx` <div id="lifetime-tcx"/>          |  The lifetime of the allocation arena. ([see more](../ty.html))
+TyCtxt <div id="tyctxt">                 |  The data structure often referred to as [tcx](#tcx) in code
 token <div id="token"/>                  |  The smallest unit of parsing. Tokens are produced after lexing ([see more](../the-parser.html)).
 [TLS] <div id="tls"/>                    |  Thread-Local Storage. Variables may be defined so that each thread has its own copy (rather than all threads sharing the variable). This has some interactions with LLVM. Not all platforms support TLS.
 trait reference <div id="trait-ref"/>    |  The name of a trait along with a suitable set of input type/lifetimes. ([see more](../traits/goals-and-clauses.html#trait-ref))