Replace obsolete finite() calls with isfinite()

Addressing https://github.com/andmarti1424/sc-im/issues/120

As mentioned in Linux's finite(2):

    Note that these functions are obsolete.

This commit requires _GNU_SOURCE, or another feature level supporting
isfinite() to be defined.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/lex.c b/src/lex.c
index 1220f4e..fc63bd4 100644
--- a/src/lex.c
+++ b/src/lex.c
@@ -229,7 +229,7 @@ int yylex() {
             if ((!dateflag && *p=='.') || ret == FNUMBER) {
                 ret = FNUMBER;
                 yylval.fval = strtod(nstart, &p);
-                if (!finite(yylval.fval))
+                if (!isfinite(yylval.fval))
                     ret = K_ERR;
                 else
                     decimal = TRUE;