other side of the signgam namespace fix: use the internal name

src/math/lgamma.c

@@ -1,10 +1,11 @@
 #include "libm.h"
 
+extern int __signgam;
 double __lgamma_r(double, int *);
 
 double lgamma(double x)
 {
-	return __lgamma_r(x, &signgam);
+	return __lgamma_r(x, &__signgam);
 }
 
 // FIXME

src/math/lgammaf.c

@@ -1,10 +1,11 @@
 #include "libm.h"
 
+extern int __signgam;
 float __lgammaf_r(float, int *);
 
 float lgammaf(float x)
 {
-	return __lgammaf_r(x, &signgam);
+	return __lgammaf_r(x, &__signgam);
 }
 
 // FIXME

src/math/lgammal.c

@@ -388,9 +388,11 @@ long double __lgammal_r(long double x, int *sg) {
 }
 #endif
 
+extern int __signgam;
+
 long double lgammal(long double x)
 {
-	return __lgammal_r(x, &signgam);
+	return __lgammal_r(x, &__signgam);
 }
 
 weak_alias(__lgammal_r, lgammal_r);