Converts a character string to a long integer.
    This function is supported on OpenVMS Integrity servers and
    Alpha only.
    Format
      #include  <stdlib.h>
      long a64l  (const char *s);
1 – Argument
 s
    Pointer to the character string that is to be converted to a long
    integer.
2 – Description
    The a64l and l64a functions are used to maintain numbers stored
    in base-64 ASCII characters as follows:
    o  a64l converts a character string to a long integer.
    o  l64a converts a long integer to a character string.
    Each character used for storing a long integer represents a
    numeric value from 0 through 63. Up to six characters can be
    used to represent a long integer.
    The characters are translated as follows:
    o  A period (.)  represents 0.
    o  A slash (/)  represents 1.
    o  The numbers 0 through 9 represent 2 through 11.
    o  Uppercase letters A through Z represent 12 through 37.
    o  Lowercase letters a through z represent 38 through 63.
    The a64l function takes a pointer to a base-64 representation,
    in which the first digit is the least significant, and returns
    a corresponding long value. If the string pointed to by the s
    parameter exceeds six characters, a64l uses only the first six
    characters.
    If the first six characters of the string contain a null
    terminator, a64l uses only characters preceding the null
    terminator.
    The a64l function translates a character string from left to
    right with the least significant number on the left, decoding
    each character as a 6-bit base-64 number.
    If s is the NULL pointer or if the string pointed to by s was
    not generated by a previous call to l64a, the behavior of a64l is
    unspecified.
    See also l64a.
3 – Return Values
    n                  Upon successful completion, the long value
                       resulting from conversion of the input string.
    0L                 Indicates that the string pointed to by s is
                       an empty string.