lib-cvs.sh: use the $( ... ) construct for command substitution

The Git CodingGuidelines prefer the $(...) construct for command
substitution instead of using the backquotes `...`.

The backquoted form is the traditional method for command
substitution, and is supported by POSIX.  However, all but the
simplest uses become complicated quickly.  In particular, embedded
command substitutions and/or the use of double quotes require
careful escaping with the backslash character.

The patch was generated by:

for _f in $(find . -name "*.sh")
do
   sed -i 's@`\(.*\)`@$(\1)@g' ${_f}
done

and then carefully proof-read.

Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>
Reviewed-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/t/lib-cvs.sh b/t/lib-cvs.sh
index 5076718..9b2bcfb 100644
--- a/t/lib-cvs.sh
+++ b/t/lib-cvs.sh
@@ -13,7 +13,7 @@
 CVS="cvs -f"
 export CVS
 
-cvsps_version=`cvsps -h 2>&1 | sed -ne 's/cvsps version //p'`
+cvsps_version=$(cvsps -h 2>&1 | sed -ne 's/cvsps version //p')
 case "$cvsps_version" in
 2.1 | 2.2*)
 	;;