pgsql: - Made several variables "const char *" instead of "char *" as

Log Message:
-----------
- Made several variables "const char *" instead of "char *" as proposed by Qingqing Zhou <zhouqq@cs.toronto.edu>.
- Replaced all strdup() calls by ECPGstrdup().

Tags:
----
REL8_1_STABLE

Modified Files:
--------------
    pgsql/src/interfaces/ecpg/ecpglib:
        connect.c (r1.26 -> r1.26.2.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/ecpglib/connect.c.diff?r1=1.26&r2=1.26.2.1)
        descriptor.c (r1.12 -> r1.12.6.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/ecpglib/descriptor.c.diff?r1=1.12&r2=1.12.6.1)
        execute.c (r1.43 -> r1.43.2.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/ecpglib/execute.c.diff?r1=1.43&r2=1.43.2.1)
        prepare.c (r1.14 -> r1.14.2.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/ecpglib/prepare.c.diff?r1=1.14&r2=1.14.2.1)
    pgsql/src/interfaces/ecpg/include:
        ecpglib.h (r1.63 -> r1.63.6.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/include/ecpglib.h.diff?r1=1.63&r2=1.63.6.1)