Tweak various scripts to improve the time they take to load

As requested in #2152, startup time should be slightly better.

rc/base/markdown.kak

@@ -25,7 +25,7 @@ evaluate-commands %sh{
   for lang in ${languages}; do
     printf 'add-highlighter shared/markdown/%s region ```\h*%s\\b   ``` regions\n' "${lang}" "${lang}"
     printf 'add-highlighter shared/markdown/%s/ default-region fill meta\n' "${lang}"
-    ref=$([ "${lang}" = kak ] && echo kakrc || echo "${lang}")
+    [ "${lang}" = kak ] && ref=kakrc || ref="${lang}"
     printf 'add-highlighter shared/markdown/%s/inner region \A```[^\\n]*\K (?=```) ref %s\n' "${lang}" "${ref}"
   done
 }

rc/base/restructuredtext.kak

@@ -18,7 +18,7 @@ evaluate-commands %sh{
               julia kak kickstart latex lisp lua makefile moon objc \
               perl pug python ragel ruby rust sass scala scss sh swift \
               tupfile yaml; do
-        ref=$(if [ "$ft" = kak ]; then echo "kakrc"; else echo "$ft"; fi)
+        if [ "$ft" = kak ]; then ref="kakrc"; else ref="$ft"; fi
         printf 'add-highlighter shared/restructuredtext/%s region %s %s ref %s\n' "$ft" '\.\.\h*'$ft'::\h*c\h*\n' '^\S' "$ref"
     done
 }

rc/core/c-family.kak

@@ -162,7 +162,7 @@ evaluate-commands %sh{
     types="char double float int long short signed size_t unsigned void"
     values="NULL"
 
-    join() { printf "%s" "$1" | tr -s ' \n' "$2"; }
+    join() { sep=$2; eval set -- $1; IFS="$sep"; echo "$*"; }
 
     # Add the language's grammar to the static completion list
     printf '%s\n' "hook global WinSetOption filetype=c %{
@@ -212,7 +212,7 @@ evaluate-commands %sh{
            nullptr_t ptrdiff_t short signed size_t unsigned void wchar_t"
     values="NULL false nullptr this true"
 
-    join() { printf "%s" "$1" | tr -s ' \n' "$2"; }
+    join() { sep=$2; eval set -- $1; IFS="$sep"; echo "$*"; }
 
     # Add the language's grammar to the static completion list
     printf %s\\n "hook global WinSetOption filetype=cpp %{
@@ -254,7 +254,7 @@ evaluate-commands %sh{
     decorators="autoreleasepool catch class end implementation interface
                 property protocol selector synchronized synthesize try"
 
-    join() { printf "%s" "$1" | tr -s ' \n' "$2"; }
+    join() { sep=$2; eval set -- $1; IFS="$sep"; echo "$*"; }
 
     # Add the language's grammar to the static completion list
     printf %s\\n "hook global WinSetOption filetype=objc %{

rc/core/kakrc.kak

@@ -40,7 +40,7 @@ evaluate-commands %sh{
     types="int bool str regex int-list str-list completions line-specs range-specs"
     values="default black red green yellow blue magenta cyan white yes no false true"
 
-    join() { printf "%s" "$1" | tr -s ' \n' "$2"; }
+    join() { sep=$2; eval set -- $1; IFS="$sep"; echo "$*"; }
 
     # Add the language's grammar to the static completion list
     printf '%s\n' "hook global WinSetOption filetype=kak %{

rc/core/sh.kak

@@ -19,7 +19,7 @@ evaluate-commands %sh{
               readonly return select set shift source test then
               time type typeset ulimit unalias until while break continue"
 
-    join() { printf "%s" "$1" | tr -s ' \n' "$2"; }
+    join() { sep=$2; eval set -- $1; IFS="$sep"; echo "$*"; }
 
     # Add the language's grammar to the static completion list
     printf %s\\n "hook global WinSetOption filetype=sh %{