s/STARTTEST/BEGINTEST/g (see #15)

Hopefully this will make Bruno happy: names now similar to
\begingroup/\endgroup.

l3build.dtx

@@ -777,7 +777,7 @@
 % \item
 % TODO: would a \cs{TESTFEXP} command (based on \cs{romannumeral} expansion) be useful as well?
 % \item
-% \cs{STARTTEST}\marg{title} \dots \cs{ENDTEST} is an environment form of
+% \cs{BEGINTEST}\marg{title} \dots \cs{ENDTEST} is an environment form of
 % \cs{TEST}, allowing verbatim material, \emph{etc.} to appear.
 % \end{itemize}
 % An example of some of these commands is shown following.
@@ -1508,7 +1508,7 @@
 % \begin{macro}
 %   {
 %     \SEPARATOR,
-%     \STARTTEST,
+%     \BEGINTEST,
 %     \ENDTEST,
 %     \TEST,
 %     \TESTEXP,
@@ -1526,7 +1526,7 @@
     ============================================================%
   }%
 }
-\protected\long\def\STARTTEST#1{%
+\protected\long\def\BEGINTEST#1{%
   \global\advance\gTESTint by 1 %
   \SEPARATOR
   \LONGTYPEOUT{TEST \the\gTESTint: \detokenize{#1}}%
@@ -1541,12 +1541,12 @@
   \LONGTYPEOUT{}%
 }
 \long\def\TEST#1#2{%
-  \STARTTEST{#1}%
+  \BEGINTEST{#1}%
   #2%
   \ENDTEST
 }
 \long\def\TESTEXP#1#2{%
-  \STARTTEST{#1}%
+  \BEGINTEST{#1}%
   \LONGTYPEOUT{#2}%
   \ENDTEST
 }