chkconfig.ltx: port some checks from trunk

- symbol is needed for some chars in unicodesymbols
- thswitch is necessary for multilingual documents containing Thai
- caption is used by our docs

lib/chkconfig.ltx

@@ -303,6 +303,7 @@
 \TestPackage{subscript}
 \TestPackage{Sweave}
 \TestPackage{textcomp}
+\TestPackage{thswitch}
 \TestPackage[turkmen.ldf]{turkmen}
 \TestPackage{ulem}
 \TestPackage{undertilde}
@@ -319,6 +320,7 @@
 \TestPackage{arydshln}
 \TestPackage{braket}
 \TestPackage{cancel}
+\TestPackage{caption}
 \TestPackage{colortbl}
 \TestPackage{diagbox}
 \TestPackage{etoolbox}
@@ -357,6 +359,7 @@
 \TestPackage{fourier}
 \TestPackage{lmodern}
 \TestPackage{luximono}
+\TestPackage[uusy.fd]{symbol}
 \TestPackage{tipa}
 \TestPackage{tipx}
 \TestPackage{tone}