It appears that it is the makeinfo from texinfo-4.8-14.el5
that causes this problem:

test -z "/usr/local/share/info" || /bin/mkdir -p "/usr/local/share/info"
 /usr/bin/install -c -m 644 ./octave.info ./octave.info-1 ./octave.info-2 ./octave.info-3 ./octave.info-4 ./octave.info-5 ./octave.info-6 ./octave.info-7 '/usr/local/share/info'
test -z "/usr/local/share/man/man1" || /bin/mkdir -p "/usr/local/share/man/man1"
 /usr/bin/install -c -m 644 mkoctfile.1 octave-config.1 octave.1 '/usr/local/share/man/man1'
../../run-octave -f -q -H ./mk_doc_cache.m doc-cache ../../scripts/DOCSTRINGS ../../src/DOCSTRINGS || { rm -f doc-cache; exit 1; }
octave_doc_rQpbyT:96: Unknown command `leq'.
octave_doc_rQpbyT:96: Misplaced {.
octave_doc_rQpbyT:96: Misplaced }.
octave_doc_rQpbyT:96: Unknown command `leq'.
octave_doc_rQpbyT:96: Misplaced {.
octave_doc_rQpbyT:96: Misplaced }.
octave_doc_rQpbyT:123: Unknown command `leq'.
octave_doc_rQpbyT:123: Misplaced {.
octave_doc_rQpbyT:123: Misplaced }.
octave_doc_rQpbyT:123: Unknown command `leq'.
octave_doc_rQpbyT:123: Misplaced {.
octave_doc_rQpbyT:123: Misplaced }.
octave_doc_rQpbyT:577: Unknown command `geq'.
octave_doc_rQpbyT:577: Misplaced {.
octave_doc_rQpbyT:577: Misplaced }.
octave_doc_rQpbyT:2121: Unknown command `geq'.
octave_doc_rQpbyT:2121: Misplaced {.
octave_doc_rQpbyT:2121: Misplaced }.
octave_doc_rQpbyT:16864: Unknown command `leq'.
octave_doc_rQpbyT:16864: Misplaced {.
octave_doc_rQpbyT:16864: Misplaced }.
octave_doc_rQpbyT:16940: Unknown command `leq'.
octave_doc_rQpbyT:16940: Misplaced {.
octave_doc_rQpbyT:16940: Misplaced }.
octave_doc_rQpbyT:17009: Unknown command `geq'.
octave_doc_rQpbyT:17009: Misplaced {.
octave_doc_rQpbyT:17009: Misplaced }.
octave_doc_rQpbyT:17044: Unknown command `geq'.
octave_doc_rQpbyT:17044: Misplaced {.
octave_doc_rQpbyT:17044: Misplaced }.
octave_doc_rQpbyT:17642: Unknown command `leq'.
octave_doc_rQpbyT:17642: Misplaced {.
octave_doc_rQpbyT:17642: Misplaced }.
octave_doc_rQpbyT:31287: Unknown command `leq'.
octave_doc_rQpbyT:31287: Misplaced {.
octave_doc_rQpbyT:31287: Misplaced }.
octave_doc_rQpbyT:31290: Unknown command `geq'.
octave_doc_rQpbyT:31290: Misplaced {.
octave_doc_rQpbyT:31290: Misplaced }.
octave_doc_rQpbyT:31340: Unknown command `leq'.
octave_doc_rQpbyT:31340: Misplaced {.
octave_doc_rQpbyT:31340: Misplaced }.
octave_doc_rQpbyT:31551: Unknown command `leq'.
octave_doc_rQpbyT:31551: Misplaced {.
octave_doc_rQpbyT:31551: Misplaced }.
octave_doc_rQpbyT:31559: Unknown command `leq'.
octave_doc_rQpbyT:31559: Misplaced {.
octave_doc_rQpbyT:31559: Misplaced }.
error: makeinfo failed with exit status 1!
error: called from:
error:   /cad/admin/linux/octave/octave-3.6.1/doc/interpreter/mk_doc_cache.m at line 68, column 3
make[4]: [doc-cache] Error 1 (ignored)